a male (usually) in a relationship with a sugar mama. so called because you keep that nigga in pocket, next to your wallet; layin on a bed of spare change, uncomfortable as shit.
The purse dog might have been laughable as a kid (with nicknames like mouth of the south coming from both other kids and adults) but he/she spent his/her entire life trying toturn the tables and get revenge on the Goliaths of his/her youth, gathering marauders for support.