Kacie is a girls' spelling of Casey, an Irish surname from Ó Cathasaigh, built on cathasach, "vigilant" or "watchful". The K and the -ie ending give it a distinctly feminine, 1980s-flavored look alongside Kasey and Kelsey. Kacie ranked number 634 in 2000, its best year in this century, and left the top 1000 in the years that followed; it stands at number 1868 in 2025, with 106 girls given the name.