Patrick Woulfe thinks Ó Muimhneacháin is more commonly Monahan in West Cork and Kerry, and a variation of Ó Muimhnigh (Moyny), a Corca Laidhe name.
The name might appear as Minahan, Manahan, or Monohan.
Minihane may have been a branch or cadet branch of Driscoll from the Beara area. See the Riobard O'Dwyer resources.
The Driscoll project agnomina page illustrates Driscoll Minihane examples.