The word “debunk” is obviously made up of the stem “bunk” and the prefix “de” which means “to remove”. The real question is where did “bunk” come from?
“Bunk” comes from the place where a lot of bunk comes from: the United States House of Representatives. In the 16th Congress (1819-1821), Felix Walker represented a district in western North Carolina, a district which included Buncombe County. This was back in the days when Representatives were actually present in the House and listened to the speeches given by other Representatives. Representative Walker carried on with a dull speech which his colleagues in the House protested. He later explained this dull speech by saying that he felt obligated “to make a speech for Buncombe.” Thus “Buncombe” became “Bunkum” when it was used in 1828 to indicate empty talk. “Bunkum” was later shortened to “bunk” and became synonymous with “claptrap.”
Walker, a Democrat-Republican (that was the name of what would become the Democratic Party), served three terms in the House. He was first elected in 1816 and he was defeated in his bid for a fourth term in 1822. When he rose to speak in 1820 the question was whether to admit Missouri to the Union as a free state or a slave state. It was the first time he had spoken on this subject and his talk was long and wearisome. He was shouted down by his colleagues, but persisted in his efforts to “make a speech for Buncombe.”
As we have come to expect with the speed of things (bunk?) coming out of Congress, the word “debunk” did not emerge for a century. Its first recorded use is in 1923.
“Claptrap,” by the way, comes to us from the eighteenth century theater where it referred to a device or a line to elicit clapping. Today, “claptrap” means “nonsense, especially pompous or important sounding nonsense.” That sort of fits into the viewpoint of Congress as the Theater of the Absurd.