Something one (usually a camp drip of a wimp) says when they've had enough of being fucked around with. Usually followed by racially motivated attack on a minor, perpatrated by said camp drip of a wimp. Alternate forms include "You need slapping down." and "You, my dear boy, are in need of a good spanking in the downward direction."
Ben was pissed off, so much so that he could've even said Bubbly's in the fridge . But instead, Ben picked up the wrench menacingly and wailed "You need slappin dahn!" before opening the proverbial can of whoop ass on Jordan.