The whistle comes from the standard message alert used on many Samsung Android phones, where a short, rising tone signalled a new text or chat message. As WhatsApp became a daily messaging app for millions of people, that same alert became closely linked in listeners' minds with an incoming WhatsApp message, even though it was a system sound rather than a tune made for the app. Shared on soundboards and reused in short videos, it stayed popular because almost everyone recognises it instantly and knows exactly what it means.