Cailyn, pronounced KAY-lin, represents a contemporary Anglicized adaptation of several Gaelic antecedents—most notably the Irish noun “cailín,” meaning “young woman,” and, by phonetic convergence, the venerable given name Caitlín, a Gaelic form of Katherine signifying “pure.” Its orthography, characterized by the medial y and terminal n, places Cailyn within the late-twentieth-century American practice of respelling traditional Celtic names to achieve both visual novelty and phonological clarity. United States birth-record data further situate the name’s sociolinguistic trajectory: first registering in federal tallies in 1979, Cailyn experienced a gradual ascent, cresting in 2011 at rank 648, and has since receded to the lower quartile of the Top 1,000, a pattern typical of neologistic spellings that enjoy an initial vogue before stabilizing as recognizable yet uncommon choices. Cognate forms—Kaylin, Kaelyn, and Caelyn—reinforce its affiliation with the broader “ay-lin” phonemic cluster, while its etymological linkage to notions of youthful femininity and purity endows the name with a semantic resonance that many Anglophone parents continue to find quietly appealing.