The correct definition of the word is actually:
Bumrush orginated when homeless peoples would come into a store and start loitering and casuing disturbances looking for places to sleep/eat/take shelter. These are stores such as super markets or retail stores. Store managers, became disgusted and tired of the homeless and degenerate roaming through their stores in search of warmth and possible indulgence of a twinkie or two. They went into the back storage room and usually took a broom and then went on a frenzying rush
to rid their stores of bums
. Thus the store went back to it's original status of a respectable and pleasant place to shop.
Clerk(to store manager): You see that guy over by the ice box... and look at that guy looking fritos off the floor in the snack aisle, I think we need to go on a bumrush.