Once upon a time, there was a plumber named "Whip" who apprenticed 8 years of his life under his father, and then he took over the family business.
Whip was a strapping young man, but as he grew older he began resembling his father and uncles more and more, putting on a gut.
As such things go, Whip worked exclusively in jeans and t-shirts and would sometimes show a bit of butt crack when he was hunched over some pipes.
The older he got, the bigger he got, until one day, a customer called Whip's son, who was also studying to take over the family business, and asked him if there wasn't something he could do to hide "Whip's crack away."