The OTT (or colloquially "the O-double-T") stands for Over The Top.
Taking the name from Sly Stallone's 1987 celluloid tour de force about a man earning his estranged son's love through arm wrestling, it is an advanced form of the Eiffel Tower Play. Instead of slapping high fives over the double stuffed ho the two gentlemen engage in an arm wrestling contest.
"Alright bro, I'm balls deep. Let's go OTT on this bitch and loser has to kiss her on the lips!"