The clip comes from That Girl by Pharrell Williams, a track from his 2006 debut solo album In My Mind. The tiny vocal interjection was later isolated by soundboard users, who repurposed the flat eh as a standalone reaction separate from the full song. Short music moments like this spread easily because they are instantly recognisable, simple to drop into edits and flexible enough for disappointment, confusion or mild disbelief. It remains in use as a compact alternative to longer reaction sounds when a creator wants the joke delivered in under a second.