Lait du laitier translates from French as milk from the milkman, a deliberately mundane phrase that became funny online through repetition and out of context use. Short French voice clips like this circulate on soundboards and in meme edits because the language barrier adds mystery for non French speakers while native speakers hear the silliness immediately. It has no widely confirmed film or show origin, so its popularity comes purely from sharing as a reaction sound, a dairy pun, and a random audio drop that can reframe any everyday clip as a joke.