It is an Irish name, and can be pronounced Kee-lee-uh (like the name Keelia) or Kee-luh. It can mean "she who sings a happy song" or "pretty girl".
-- Anonymous User 12/19/2005
If it were a feminine form of Kelly, then it should mean "war", "strife", or "bright-headed", depending on the source. It seems too insubstantial to me, like a manufactured name.