A modern spelling of Caitlin or Kaitlyn, derived from Katherine and meaning "pure."
Katlyn is a variant spelling of Caitlin, the Irish form of Catherine, which itself traces back through Old French Catherine to the Latin Catharina and ultimately to the Greek name Aikaterine. The Greek etymology remains debated: some scholars link it to the goddess Hecate, others to a root meaning "pure" (katharos), and it is the latter meaning — purity, clarity — that became the dominant symbolic interpretation in Christian Europe, where Saint Catherine of Alexandria (martyred circa 305 CE) made the name a byword for wisdom and faith. The name spread throughout medieval Europe with extraordinary speed, carried by the prestige of the saint and later by figures like Catherine of Siena and Catherine of Aragon.
The Irish form Caitlín emerged as Gaelic phonology processed the borrowed name through its own sound system, producing a pronunciation — roughly "KOTCH-leen" — that bewildered English speakers for centuries. When Irish emigration brought the name to the English-speaking world in large numbers, spelling variants proliferated as parents tried to capture the sound in writing: Cathleen, Kathleen, Kaitlin, Kaitlyn, Katelyn, and Katlyn all emerged as attempts to render the Irish phonology in English orthography. Katlyn, with its clean brevity and the modern preference for economical spelling, arrived as one of the leaner variants.
The name surged dramatically in the United States in the 1980s and 1990s, when Kaitlyn and its variants became among the most popular girls' names in the country. Katlyn sits in this wave — recognizable, feminine, and softened from its ancient origins to something that feels thoroughly contemporary. It carries centuries of history lightly, arriving in modern nurseries stripped of religious connotation but still bearing the particular grace of a name that has survived, in one form or another, for nearly two millennia.