Source : Webster's Revised Unabridged Dictionary (1913)

Mother-naked \Moth"er-na`ked\, a.
   Naked as when born.

Source : WordNet®

mother-naked
     adj : as naked as at birth [syn: {naked as the day one was born},
           {naked as the day you were born}, {in one's birthday
           suit}, {in your birthday suit}]