rá-tim-bum

Etymology
. It may have originated among alumni of the as a corruption of " Timbum", referring to a rajah who purportedly visited the institution, or from an onomatopoeic imitation of the sound produced by a fanfare, such as the snare drum ("rá"), the cymbals ("tim") and the bass drum ("bum").

Interjection

 * 1)  Sung or shouted at the conclusion of a happy birthday song or similar celebration.