Kailey is one of many spellings of Kaylee, a modern English name usually explained as a blend of Kay and Lee; it is sometimes linked to the Irish surname Ó Caollaidhe, from caol, "slender". The ai spelling echoes Hailey and Bailey. In the United States Kailey ranked number 305 in 2000, peaked at number 228 in 2004 and has declined steadily since, leaving the top 1000 in 2022 and standing at number 1420 in 2025.