Kay

Proper noun

 * 1)  derived from several Old and Middle English words; also adopted by immigrants whose surnames began with a K.
 * 2)  derived from the surnames, or from a rare medieval given name (as the Sir Kay of Arthurian legend), Welsh Cai, Latinized as Caius, related to the modern male name Kai.
 * 3) A short form of Katherine and other female names beginning with a "K"; popular as a middle name.