No confirmed original recording, film or creator is attached to Gros Mongooole, so its history is mainly online rather than in a single source work. The phrase itself is French slang built on gros mongol, a playground insult, and the stretched pronunciation is what turned it into a shareable soundboard clip. Short French voice reactions like this spread through meme pages, Discord servers and chat groups, where a two second shout is easier to reuse than a full video. It stays popular because it signals teasing disbelief instantly, even for listeners who speak little French.