The phrase 'who da fook' comes from the longer viral question 'who da fook is dis,' a piece of internet slang mocking a thick accent while calling out an unknown person. It spread through reaction videos, gaming clips and short-form edits where creators needed a fast way to question someone's presence. Because the delivery is more theatrical than hostile, it stuck around as a reusable punchline. Today it lives mostly on soundboards, dropped into memes whenever an unfamiliar face or an absurd statement needs an instant, funny challenge.