This girl's name, also used as a boy's name, is used in Gaelic as McKenna. McKenna is a surname meaning 'son of Cionnaith' but as a first name, Makenna, it means "happiness". It's popularity stems from the fact that it sounds like the popular Hebrew derived name Michaela (or McKayla) and the popular Scottish surname name Mackenzie.

Alternative spellings:
McKenna, Mackenna

Common nicknames:
Mac, Kenna, Macy, Mickey, Anna, Mik

The name McKenna in Ireland is derived from the native Gaelic Mac Cionaoith Sept who were a branch of the Ui Neill Sept and were located in County Monaghan.
You can find the crest here.