Kaitlyn is the American phonetic spelling of Caitlín, the Irish form of Catherine, which goes back to the Greek Aikaterine and is usually linked to katharos, "pure". The K spelling took off in the United States in the 1980s and for a while outsold the original. Kaitlyn was a top 100 name in 2000 at number 30, then slid out of the top 100 and down to number 802 in 2025.