Orginin - South African
Derived from a childrens' song designed to tease fat people tilted "Hey Fatty Boomsticks".
Lyrics - 'Hey Fatty boomsticks...sweet sugar dumplings...just because you're so big and fat...don't think I'm afraid of that....hey fatty boomsticks....sweet sugar dumplings....
Believed to reference the size of the legs of the fat person (their sticks). Which make a boom boom sound each time they take a step - thus fatty boom sticks
Hey, fatty boomsticks, out the way, you're blocking the light (sun).
We better all get some food before boomsticks gets here or there won't be any left.