What is the meaning of the name Mckenna?

MacKenzie is a common Scottish surname, traditionally denoting membership in the MacKenzie clan. The MacKenzies have been a significant clan in Scotland for at least 700 years.

MacKenzie itself is an Anglicization of the Gaelic MacCoinneach, "son of Coinneach."

The Mac- prefix in Scottish names means "son of."

Coinneach is derived from cainneach (fair one; handsome). Hence: "son of the bright one".

The spelling Mackenzie is a popular variant for the first name.

Another answer:

Mackenzie is of Scottish origin meaning 'son of Kenneth.'