Kayce is a modern American spelling of Casey, which comes from the Irish surname Ó Cathasaigh and means "vigilant" or "watchful". The spelling with a K was all but unknown until Kayce Dutton, the ranch-hand son on the TV series Yellowstone, which premiered in 2018, turned it into a Western-flavored boys' name. Kayce entered the US top 1000 in 2022 and has climbed to number 375 in 2025, its best rank yet.