The first name Cay is female and male.
The origin of the name Cay as a form of Kay is not clear. It is presumably a Frisian short form of Gerard or Nikolaus, but as well of the Latin name Cajetanus and is of Celtic origin. It is a name for boys and seldom for girls (from Latin Cajetana or Katharina).
Cay means “warrior” (from Frisian “kempe”), “victory of the people” (from Nikolaus), “spear strength”, “strong with the spear” (from Gerard), “from the town Gaeta” (from Cajetanus), in Celtic “spear bearer/thrower”. For girls, Cay means “from the town Gaeta” (from Cajetana) or “pure” (from Katharina).