I grew up in a family wary of anything overtly Christian. My father transformed the expression “cross your fingers” into “star your fingers” because, as he used to explain, crosses are Christian and thus not for Jews. Yet at the same time, my mother taught me to write “x” and “o”—a kiss and a hug—after my signature. So deeply embedded was this English-language tradition that I am sure it never crossed her mind—she was a proper Jewish mom as well as the executive director of the Jewish Community Center—that the “x” might have anything to do with a cross.

I never thought about it myself until she passed away in 2012 and I began to emit streams of “x’s” and “o’s” like a binary love code in the countless personal and professional emails that consume much of my daily life. Suddenly I became curious about where these symbols come from, these ur-emoticons that English speakers of all faiths sprinkle so liberally across our correspondence.

The Internet abounds with origin theories of all kinds. I found visual explanations: that “x” resembles a kiss; “o” looks like an embrace; and together “x” and “o” form a kiss on a face. Then there were auditory
associations such as the similarity in the pronunciation of “x” and “kiss.” But it very quickly became apparent that x most likely evolved from the written tradition. A simple, easily drawn shape, it entered the Western alphabet as the ancient Phoenician letter samekh for the consonant sound “s.” In early Hebrew it was the letter taw and makes an appearance in the Book of Ezekiel as a mark set “upon the foreheads” to distinguish the good men of Jerusalem from the bad.

When Christianity came along, it co-opted the “x.” “In Christian texts, one abbreviation of the Greek word Christos—meaning messiah—used the first two Greek letters of Christos, chi (X) and rho (P), combined into one shape,” says Stephen Goranson, a historian of religion at Duke University who studies the etymology of symbols and words. “So both orientations of crossed lines—X shape and the more-or-less lower case T shape—took on religious significance among Christians.” No one knows exactly how this happened: One story is that in 312 CE the Roman Emperor Constantine saw the chi-rho in a dream in which God told him “in this sign you will conquer.” Constantine went on to legalize Christianity, which later became the official religion of Rome.

Once it was a sacred symbol, the “x” came to mean “faith and fidelity,” says Marcel Danesi, a professor of linguistic anthropology and semiotics at the University of Toronto. From there it became the signature of choice in the Middle Ages, a time when few people could write and documents were sealed with an x embossed in wax or lead. During that period, it was customary to close books with a kiss, and oaths of political and economic fealty between kings and their vassals were “sealed with a kiss”— an early antecedent of the acronym SWAK, which became popular during World War I for soldiers to imprint on their letters home. (My mother also taught me to write SWAK across the flaps of envelopes before mailing letters.)

“Symbols have a way of jumping from one domain to another,” says Danesi, who wrote The History of the Kiss: The Birth of Popular Culture, “and it’s a small step to come from sealing a letter to sealing a love affair.” He speculates that “x” underwent a conversion in an act of medieval romantic rebellion. “Romantic love becomes an obsession, and the kiss became empowering. It said to family and society: ‘You can’t tell me whom I should marry.’” This may have been particularly true for women, who had less say than men over the choice of a lover. “The kiss became, ‘If I kiss that man, then this is the man I love and want,’” says Danesi. “So much was packed into that symbol of a kiss… it has become a kind of collective memory. We use x, even if we don’t know why.”

No one knows when “x” was first written to mean a kiss, but The Oxford English Dictionary says the earliest known use was by British curate and naturalist Gilbert White in a 1763 letter that ended:

 “I am with many a xxxxxxx and many a Pater noster and Ave Maria, Gil White.”

Stephen Goranson disagrees with the OED. “The x’s in White’s letter could possibly mean kisses, but it is more likely they meant blessings,” he says. Their juxtaposition with “Ave Maria” is reminiscent of the 1719 use of “x” in Robinson Crusoe, in which Daniel Defoe explicitly writes that crosses mean blessings. Goranson explains that blessings and kisses have been intertwined in the human psyche for all of history. “Mystics went back and forth on the love of God and love of a beloved spouse going way back,” he says. “Just look at The Song of Songs. The same song could be one person’s devotional hymn and another’s love poem.” Another example is A Woman of Valor, the Hebrew poem recited by Jewish husbands to their wives prior to the Sabbath evening meal that is also understood to be an expression of love of God.

Clear references to “x” as kisses, says Goranson, don’t appear until more than a century later. Goranson points out a later OED citation, an 1894 letter by Winston Churchill to his mother. “Please excuse bad writing as I am in an awful hurry. (Many kisses.) xxx WSC.” In his own research, Goranson found several citations from 1880 on, such as a poem published in 1893: “Why do our sweet sentimental young misses / In love letters make little crosses for kisses?”

X

Christianity came along and co-opted the “x.” It became an abbreviation of the Greek word Christos— which means messiah.

How and when “o” came to signify a hug is another big question. “It’s fairly safe to say that ‘x’ meaning kisses appeared in letters by itself before the ‘o,’ and that hugs were added to kisses,” says Goranson.

In my search I ran across an unexpected Yiddish angle—an oft-quoted “o” theory postulated by none other than the late Leo Rosten in his 1968 book The Joys of Yiddish. Rosten suggests that the “o” may have evolved as a signature in connection with the evolution of the word “kike.” When Jewish immigrants who could not write in Latin script arrived at Ellis Island, they refused to sign entry forms with the customary “x,” which they interpreted as a crucifix and a symbol of oppression. Instead, they drew an “o,” leading immigration inspectors to call anyone who signed with an “o” “a kikel [circle in Yiddish] or kikeleh [little circle], which was shortened to kike,” and eventually took on a derogatory meaning.

Fascinating, to be sure, but I was unable to confirm this theory, try as I might with researchers at the American Jewish Historical Society and the YIVO Institute of Jewish Research, historians and genealogists, several of whom considered it “apocryphal.” In his book, Rosten attributes this information to Philip Cowen, an immigration inspector at Ellis Island. While no one can say for sure it is not true, Cowen did not mention it in his 1932 autobiography, Memories of an American Jew, and there are no records of entry forms that needed to be signed, says Barry Moreno, an Ellis Island researcher and author of the Encyclopedia of Ellis Island.

But the timing—late-19th and early-20th century—of the debut of the “o” for hug may, however, be close. According to the research of linguist Ben Zimmer, executive producer of vocabulary.com and language columnist for The Wall Street Journal, the earliest mention of an “o” for hugs is 1905. His search of online databases came up with a 1905 Missouri Supreme Court case—The State v. James E. Kelley. Among the evidence was this letter:

“10,000  million X O
Yours forever
I will kiss Cicil for you now.”

And the court record added:

“Prosecutrix, her mother and a banker in Bolivar testified that this letter was in defendant’s handwriting. Prosecutrix also testified that defendant told her that when he wrote X and O he meant hugs and kisses.”

Even if “o” came to mean hug at the end of the 19th century, how it united with “x” to form “xo” remains a mystery. One hypothesis is that the ubiquitous game of tic tac toe, played by children for millennia, brought them together. Known as noughts [zeros] and crosses in England, and mill, merels and morris throughout history, the game has roots in ancient Egypt and Rome. The game—originally played with pebbles or coins—only incorporated the “x” and the circle when paper became plentiful, says game historian David Parlett, author of The Oxford History of Board Games. “These are two of the simplest contrasting symbols, easy to master by illiterate people.” Parlett is unsure how tic tac toe’s cross and circle could have metamorphosed into hugs and kisses, although he says the Roman poet Ovid once referred to the game of mill in a love poem.

Ben Zimmer ventures a guess that the pairing of “x” and “o” in noughts and crosses may have led to the addition of “o” to “x.” Just as noughts and crosses go together, so do hugs and kisses. “At some time ‘x’ stood for kisses and if you wanted to expand that to hugs and kisses ‘o’ became a reasonable choice,” he says. Another possibility is that the “o” was added because it is iconic, that is, a symbol that is a representation of the thing itself. Zimmer also adds that there are those who believe the “o” stands for kiss and “x” for hugs, which may stem from the fact that we say “hugs and kisses” as opposed to “kisses and hugs.” This, he says, is contrary to the historical record: It is likely that we say hugs first because it has fewer syllables. In English, paired phrases usually start with the shorter word and end with the longer.

O

Leo Rosten suggests that the “o” may have evolved in connection with the evolution of the word “kike.”

Whatever their backstories, “x” and “o” are deeply embedded popular culture images connected to love and are used by both men and women. Online, they flourish alongside countless emoticons and acronyms such as BFF—Best Friends Forever. In a recent study of 14,000 Twitter users, researchers found that “xo,” “xoxo” and “xoxoxo” are reflective of a kind of relationship or create a kind of relationship. Tyler Schnoebelen, a linguist with a Ph.D. from Stanford who is the founder and chief analyst of Idibon, a start-up in San Francisco that analyzes social media, warns against simplifying their use in terms of gender. “They are particularly popular among two clusters of tweeters, he says. “The first talks a lot about people—kids and husbands, in particular, and the other talks a lot about social media and music. Both of these groups are mostly women. But other groups that are mostly women do not use very many ‘xo’s.’”

A recent spate of articles has highlighted the usage of “x” and “o” by smart, prominent women such as Diane Sawyer and Arianna Huffington, who sign off from emails with “xo.” Critics deride the usage as girlish, while defenders point out that “x” and “o” are useful tools for women to soften direct requests, in the same way that men traditionally use humor.

“‘X’ and ‘o’ are part of a whole array of symbols among girls and women that have one thing in common: They are expressive,” says Deborah Tannen, professor of linguistics at Georgetown University and author of You Just Don’t Understand: Women and Men in Conversation. These include abundant use of exclamation points and of capital letters. “Girls and women have to show a certain level of enthusiasm to seem sincere,” she says. “If they don’t, it comes across to other girls and women as cold or rejecting.”

Will “x” and “o” continue to be picked up by new generations? Online, they may be vulnerable. “Today, 15-year-old girls around the world have new emoticons for love,” says Scott Fahlman, Carnegie Mellon professor of language technologies and computer science, who is credited with inventing the original smiley face emoticon 🙂 to denote sarcasm. “One version is a <3 forming a heart.” A quick look at social media reveals that “<3” is popular among adults as well. Standard alphabetical characters, however, are being replaced by computer-generated graphics. And soon, Fahlman says, these graphic emoticons may be replaced by video images. “There’s no reason now we can’t send a personal video image of a hug and a kiss with one click.”

No newfangled emoticons for me, thank you. I intend to continue to sign off with “xo.” “X” and “o” may have come down through time laden with feudal and religious baggage, but, as Deborah Tannen told me, “Symbols are not their etymologies but what they mean today.” For me they will always be associated with the warmth and love of my beautiful mom. They are a way to pass that affection on. XO!