Little is documented about where My Day Mo Koh first came from, so its history is really about how it circulates online as a short meme sound. Shared as a 12 second clip on soundboards, it gets reused because the phrase is easy to recognise even without context and works detached from any original scene. Creators pull it into edits, chats and short videos when they need an upbeat vocal cue that signals a joke is coming, and its small file length makes it easy to drop in repeatedly.