Kaylin is a modern American name formed from Kay and the ending -lin, and it also serves as a spelling of Caitlin, the Irish form of Katherine, which is usually read as "pure". It was at its most popular around the turn of the century: number 450 in 2000 and a peak at number 371 in 2009, followed by a steady slide to number 1644 in 2025, with 126 girls.