The line comes from Full Metal Jacket, Stanley Kubrick's 1987 war film, where R. Lee Ermey plays the unforgiving drill instructor Sergeant Hartman. In the Italian dub, Hartman's dismissal is delivered as Buonanotte signorine, and that version has circulated on soundboards and in short meme edits as a curt, ironic farewell. Its staying power comes from the contrast between the polite Italian greeting and Hartman's reputation for relentless shouting, which makes a simple goodnight feel like an order. Fans reuse it because the reference is instantly understood even without seeing the film.