n. (1988)
A pejorative term used mostly in fight scenes. It is likely a variant of butthole. Coined by Gary Busey's character Frank McBain in the Cold Warthriller 'Bulletproof'.
A Buttcorn Kernel is what describes that itchy feeling in your butt after you thought you had wiped properly earlier but actually did not. It feels almost like there are popcorn kernels in your sphincter; and it sure does itch.
"Damn dude...I got some serious buttcorn kernels right now."