In the poker variant of Texas Hold 'em, Dog Balls refers to holding pocket 8's (two 8's) as your hole cards. Superstitiously viewed as an unusually difficult hand to crack(beat).
when your nuts get behind your thighs on the butthole side when your legs are closed. kinda of like "the brain" but instead of using your hand your legs are doing the work. very inconvenient when you sit down or someone hits you from behind.