it seems likely that this was born from a 'Friends' episode in which character Chandler Bing uses "WooPAH!" in a feeble attempt at replicating the sound of a whip. Thusly, one might say "woopah" when making someone or something their bitch.
Synonyms for woopah
On this page, you will find 30 slang terms related to woopah. Some of the top words include: onna, bustin' some tail-skins, Zoink, ners, How YOU doin'?, and 25 more.