One theory to explain the occurrence of a hole in the crotch of a mans jeans. Over time the material is eroded by the constant friction of the swinging ball bag.
Person 1: 'Dude, your nuts are hanging out of that hole in your jeans'.....
Person 2: 'Yeah sorry man, ball bag friction theory'
Person 2: 'Yeah sorry man, ball bag friction theory'
by Yippikiai June 9, 2013
Get the Ball bag friction theorymug.