The phrase is simply French for a hesitant 'um... no', with 'heu' used like a filler sound while thinking and 'non' meaning no. Short hesitant clips like this circulate on user soundboards because the meaning is clear even without context, and the 0.7 second length makes the line easy to drop into chats, streams and edits. It has stayed useful as a reaction sound rather than a quote from a known scene, letting creators borrow the awkward pause for refusals, rejections and uncomfortable answers in many different situations.