Kaylen is a modern American name formed from Kay with the ending -len, and it is usually read as a variant of Kaylin or Kaelyn, meaning "pure" after Katherine or "slender" after the Irish Caoilfhinn. It belongs to the large family of Kay- names that flourished in the 2000s. Kaylen entered the US top 1000 for girls in 2003, peaked at number 688 in 2009 and has declined to number 2796 in 2025.