Could it possibly be related to Stallone, as in the surname, meaning stallion? Maybe a pet form?
It seems to be in use as a surname though and could come from that.
Another interesting thing I found was that Stallo is the
Santa Claus figure of the Saami people - "a giant horned and hairy wildman" Apparently in Lappish Stallo means 'metal man' (referring to his dress)
http://www.forteantimes.com/articles/192_lapp2.shtml