(used to indicate the sound of a blow, collision, falling object, etc.).
immense energy; vigor: a movie with plenty of whammo to please the kids.
characterized by such a strong effect: a show with a whammo ending.
Origin of whammo
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
exclamation signifying violence or surprise, 1932, from wham (q.v.).
Online Etymology Dictionary, © 2010 Douglas Harper