The word debunk was prominently coined by author William Woodward in his 1923 satirical novel Bunk, wherein the main character went around trying to "take the bunk out of things". The bunk in that sentence is with the meaning of "nonsense" that we still sometimes use today. That's a 1900 shortening of bunkum, which is a misspelling of Buncombe, the name of a county in North Carolina. The area got associated with nonsense because of a particularly boring speech given by Democratic-Republican Congressman Felix Walker concerning the admission of Missouri to the Union. Despite being asked multiple times to stop his excruciating drivel, Walker kept on talking, saying it wasn't for the benefit of Congress but rather a "speech for Buncombe", irrevocably associating his town with political verbiage. This is completely unrelated to the "type of bed" definition for bunk, which is related to bunker.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.