A spelling variant of Cassie, usually derived from Cassandra, a Greek name meaning "she who excels over men."
Casie is a variant spelling of Casey, a name with Irish roots running back to the Gaelic surname Ó Cathasaigh, meaning "descendant of Cathasach." Cathasach itself derives from cath (battle, vigilance) and carries connotations of watchfulness and alertness — qualities prized in Irish culture where the surname tradition encoded a family's defining characteristics. The O'Casey sept was historically based in County Dublin and County Roscommon, and the anglicized form Casey traveled widely during the Irish diaspora of the nineteenth and twentieth centuries.
In American culture, Casey took on a life far beyond its Irish ethnic origins, becoming a name associated with quintessential American folk heroism through two famous stories. "Casey at the Bat," Ernest Thayer's 1888 comic ballad about a baseball player's arrogant strikeout, made Casey a symbol of hubris meeting its comeuppance — beloved precisely because it punctures self-importance. Then Casey Jones, the locomotive engineer who died in 1900 keeping his hand on the throttle to slow a crashing train, became a folk hero of working-class dedication, immortalized in songs and ballads.
These two Caseys gave the name a distinctly American texture: sporty, rugged, and a little larger than life. The spelling Casie represents the twentieth century's widespread practice of giving familiar names feminine specificity through altered orthography — the -ie ending signals a feminine bearer in a name that had become gender-neutral. Today Casie feels warm and accessible, a name with deep Irish roots and a thoroughly American accent, carrying just enough familiarity to feel like home and enough individuality to stand out in a classroom.