English pet name for Michaela or Michelle, feminine forms of Michael, from the Hebrew name Micah, "one who is like God".

When used as a given name the spelling Mikki is often preferred.

While Mickey is normally a pet-name for Michelle or Michaela, one correspondent [GH] notes that his mother, called Margaret and of Scottish descent, was known as Mick or Mickey. We don't know if these are common pet names for Margaret.