The line comes from Mad Max: Fury Road, released in 2015, where the War Boys, the pale, fanatical fighters serving Immortan Joe, shout Witness Me as they launch themselves into a glorious death in battle, believing it will carry them to Valhalla. Clips of the shout spread through film edits, reaction videos and gaming montages, where it became shorthand for going all in despite the obvious risk. It endures because the delivery is instantly recognisable and works for both heroic moments and self-aware jokes about overconfidence.