Is it ensure, insure, or assure?
1923, from de- + bunk (n.2); first used by U.S. novelist William Woodward (1874-1950), the notion being "to take the bunk out of things." Related: Debunked; debunking.
Toclearawaylies,exaggerations,vanities,etc: The author neither glorifies nor debunks
[1923+; coined by W W Woodward in a book published in 1923]