The shout comes from the late 1990s Wassup craze, started by Budweiser adverts where friends greeted each other on the phone with an exaggerated wassup. Scary Movie in 2000 parodied the advert and stretched it into wazaaa, which became the version most people imitated. The phrase spread through schoolyards, ringtones and early internet forums, then returned as a soundboard staple. It survives because one stretched syllable instantly signals a goofy greeting, making it perfect for reactions and prank edits without any setup.