The use of the letter X to signify a kiss is one of the most recognisable conventions in written communication in the English-speaking world. Commonly found at the end of personal letters, greeting cards and digital messages, the symbol X functions as a shorthand expression of affection, intimacy, or goodwill. Despite its ubiquity, the origins of this practice are not entirely straightforward and scholars have proposed several overlapping explanations grounded in medieval literacy practices, religious symbolism and visual analogy. This essay explores the historical development of the “X as a kiss” convention, examining how the symbol emerged from medieval signing practices, the role of Christian symbolism and the gradual cultural reinterpretation of the mark into a gesture of affection. Together, these factors help explain how a simple letter came to represent a deeply human act.
Medieval signatures and the cross mark
One of the most widely cited explanations for the use of X as a kiss lies in medieval practices surrounding signatures and oaths. During the Middle Ages, literacy rates in Europe were relatively low and many individuals were unable to write their names. When signing legal documents, contracts, or letters, those who could not write would often mark the document with a simple cross. This cross, which resembled the letter X, served as a substitute signature. However, the cross was not merely a practical mark; it also carried strong religious significance. In Christian Europe, the cross symbolised faith and truth and placing such a mark on a document implied that the signer affirmed the statement before God.
To reinforce the sincerity of this act, it was common practice for the signer to kiss the cross after making it. The kiss functioned as a physical gesture of reverence and commitment, similar to kissing a Bible during an oath. Over time, the cross mark and the accompanying kiss became associated in people’s minds. When letters began to circulate more widely, particularly in personal correspondence, the cross mark could evoke the idea of that ritualised kiss. Consequently, the X came to symbolise the act itself rather than merely the religious mark. In this interpretation, the symbol is not originally a representation of lips but rather the remnant of a devotional practice embedded within medieval documentary culture.
Religious symbolism and sincerity
This religious explanation is supported by historical references to the phrase “signing with a cross”. In legal documents dating from the late medieval and early modern periods, scribes frequently recorded that an illiterate individual “made his mark” or “signed with a cross”. The cross therefore operated as both a signature and a moral guarantee. In a society where religion permeated everyday life, the act of kissing the cross reinforced the legitimacy of the agreement. As literacy increased in later centuries, people who could write their names sometimes continued to include crosses in correspondence as a symbolic expression of sincerity or blessing. Gradually, the religious connotations weakened, allowing the symbol to be reinterpreted in a more secular, affectionate context.
Visual resemblance and pictographic interpretation
Another explanation for the association between X and a kiss concerns visual resemblance. Some scholars suggest that the symbol resembles the shape of two pairs of lips touching, particularly when drawn with slightly curved lines. In this view, the letter X acts as a stylised pictogram rather than a symbolic inheritance from religious practice. Visual shorthand has long played a role in written communication; for example, the heart symbol represents love despite bearing little anatomical resemblance to the human heart. It is therefore plausible that writers adopted the cross-shaped mark as a convenient graphic representation of a kiss.
However, the visual resemblance theory alone does not fully explain why the convention became widespread specifically in English-language correspondence. Many symbols resemble other shapes, yet only a few develop stable cultural meanings. The historical evidence of cross-signing and cross-kissing provides a stronger documented foundation for the practice. Consequently, many historians argue that the visual interpretation of X as lips may have emerged later, reinforcing an existing convention rather than creating it.
The rise of letter-writing culture
The development of the “X as a kiss” convention is also closely linked to the evolution of letter-writing culture. Personal correspondence expanded significantly from the seventeenth century onwards, particularly among the middle classes. Letters became an important medium for maintaining relationships across distance, whether between family members, friends, or romantic partners. In such contexts, writers often sought ways to express warmth or affection within the constraints of written language. The addition of small symbolic marks provided an efficient way to convey emotional tone.
By the nineteenth century, the practice of ending letters with one or more Xs had become increasingly common in Britain. Etiquette manuals and personal letters from the period show that the symbol functioned as a gesture of intimacy, typically used between close acquaintances or relatives. The number of Xs could vary depending on the level of affection the writer wished to express. A single X might indicate polite friendliness, while multiple Xs suggested stronger emotional warmth. This flexible system allowed writers to nuance their communication without altering the formal structure of X itself.
The emergence of “XOXO”
The complementary use of the letter O to represent a hug emerged later, particularly in North American contexts. Unlike the X, the origin of the O is less clearly tied to medieval practice. Some scholars argue that the O resembles the shape of arms encircling another person, making it an intuitive symbol for an embrace. Others suggest that the pairing of X and O simply developed as a balanced visual pattern, with the circle complementing the cross. Regardless of its origin, the combination “XOXO” eventually became a widely recognised shorthand for “hugs and kisses”, especially in informal communication.
Technology and the persistence of the symbol
Technological changes have also played a role in preserving and spreading the tradition. The rise of telegraphy in the nineteenth century encouraged brevity, prompting writers to rely more heavily on symbolic shorthand. Later, the emergence of greeting cards, postcards and eventually electronic messaging reinforced the habit of ending messages with affectionate symbols. In contemporary digital communication, Xs remain common in text messages, emails and social media posts, particularly in British usage. The symbol continues to function as a marker of friendliness or affection, even though many users are unaware of its historical origins.
Cultural variation and interpretation
Regional differences in interpretation also illustrate how cultural conventions evolve. In the United Kingdom, placing an X at the end of a message is generally perceived as friendly and informal, often used among friends, family members, or colleagues who share a relaxed relationship. In contrast, some other English-speaking cultures use the symbol less frequently or interpret it as more overtly romantic. These differences highlight the importance of social context in determining the meaning of written symbols. The X itself has no intrinsic emotional content; its significance derives from shared cultural understanding.
From gesture to symbol
The persistence of the X symbol also reflects the broader human tendency to translate physical gestures into written form. Communication scholars often note that writing attempts to replicate aspects of spoken or embodied interaction. In face-to-face encounters, affection may be conveyed through gestures such as a kiss on the cheek or a warm embrace. When communication shifts to a written medium, individuals often seek alternative ways to express similar sentiments. Symbols such as X therefore serve as substitutes for physical acts of affection, bridging the gap between embodied and textual communication.
X beyond the kiss
It is also worth noting that the letter X has historically carried multiple symbolic meanings beyond its association with a kiss. In mathematics and science, it frequently represents an unknown quantity. In cartography, it may mark a specific location, as in the phrase “X marks the spot”. In Christian iconography, it has sometimes been used as an abbreviation for the name of Christ, derived from the Greek letter chi (Χ). The ability of a single symbol to acquire multiple meanings across different contexts demonstrates the flexibility of written language and the role of cultural convention in shaping interpretation.
Conclusion
Despite the variety of explanations proposed, most historians agree that the “kiss” meaning likely developed through a gradual process rather than a single decisive event. Medieval cross-signing practices provided the initial association between the mark and a ritual kiss. As literacy expanded and religious practices evolved, the symbol became detached from its strictly devotional context. Writers then reinterpreted the mark as a sign of personal affection within informal correspondence. Over time, the meaning stabilised through repeated use, eventually becoming a standard convention in English-language communication.
In conclusion, the use of the letter X to represent a kiss reflects a complex interplay of historical, religious and cultural influences. Its origins can be traced to medieval practices in which individuals signed documents with a cross and sealed their commitment by kissing the mark. This ritual created a symbolic association between the cross-shaped sign and the act of kissing. As literacy increased and letter-writing became more widespread, the symbol was gradually incorporated into personal correspondence as a gesture of affection. Later interpretations, including the visual resemblance between the X and the meeting of lips, may have reinforced the convention, helping it persist into modern times. Today, the humble X continues to function as a small yet meaningful token of warmth in written communication, demonstrating how historical practices can shape everyday language in subtle and enduring ways.