The phrase comes from the closing moments of “The Next Episode” by Dr. Dre featuring Snoop Dogg, Kurupt and Nate Dogg, released in 1999 on the album 2001. Online, the ending line became a standalone reaction sound and spread through memes, short edits and soundboards for years. It stayed popular because the delivery is so instantly recognisable and because it works as a comedic button, much like the Inception Button does for dramatic emphasis.