The "West Coast" part refers to the fact that Pork-chops come from the west coast of Europe.
The "Chopper" part is short for pork-chop, another derogatory term towards Portuguese people.
Oscar: What up?
Jerome: Fuck you, you fucking West Coast Chopper piece of shit!
Oscar: Shut the fuck up nigger!
Additionally, the ankles can be twisted for that extra bit of immersion.