Of Scottish origin but now widely used in the English-speaking world. It is derived from a topographic term denoting a narrow strait or channel and in part is a transferred use of the surname, a local name from the region in Ayrshire so called. As a girl's name it appears to have been largely superseded by Kyla.
English (of Norman origin): habitational name from places called Monceaux, in Calvados and Orne, or Monchaux, in Nord and Seine-Maritime. These get their name from the plural form of Old French moncel ‘hillock’, Late Latin monticellum, a diminutive of mons. Compare Mont.