I've just had a look in my copy of Farmer & Henley - Slang and its Analogues Past and Present (1909) and one of the meaning of Bow-Wow is given as: 2. (old).- A Bostonian: in contempt.

In the context of the song, this is a possible meaning for it.

Although listed as old it doesn't specify how old; perhaps an American can find us a date for that.

Mick