Meaning From Celtic origin meaning 'descendant of Cathasaigh, descendant of the vigilant one'. Origin of Cassey Celtic , Irish Popular Middle Names Rumor Pronunciation 🔊 Listen Cassey CAS-ee Similar Names Kaycee Kasie Kaycie Kacie Kacy Kaci Kacey Kaylaugh Caley Arlene Year by Year Popularity of Cassey