An Etymological Dictionary of the German Language/Annotated/Mieze
Mieze, feminine, ‘pussy,’ Modern High German only; it is either the modern Bavarian pet name for Maria, ‘Mary,’ just as Hinz, the pet name for the tom-cat, is connected with Heinrich, ‘Henry,’ or it is a recent onomatopoetic form like the phonetically cognate Ital micio, and the corresponding Romance class. The Modern High German mianuen, mauen, are also onomatopoetic forme.