Source : Webster's Revised Unabridged Dictionary (1913)

Nanny \Nan"ny\, n.
   A diminutive of Ann or Anne, the proper name.

   {Nanny goat}, a female goat. [Colloq.]

Source : WordNet®

nanny
     n 1: a woman who is the custodian of children [syn: {nursemaid},
          {nurse}]
     2: female goat [syn: {nanny-goat}, {she-goat}]