The line comes from the 2005 comedy Wedding Crashers, where Vince Vaughn plays Jeremy Grey, one half of a pair of friends who crash weddings for fun. In the film, taking a grenade means stepping in to distract an unwanted guest so a friend can escape, a piece of wedding-crashing slang that turns an awkward social duty into a military joke. The short clip circulates as a reaction sound for loyalty and self-sacrifice, and it still works because the exaggeration is instantly recognisable to anyone who has taken one for the team.