"Debunk" comes from "bunk/bunkum" (slang for nonsense, senseless talk), itself from Buncombe County:
From buncombe, from “speaking to (or for) Buncombe County, North Carolina”, a county in North Carolina named for Edward Buncombe. In 1820, Felix Walker, who represented the county in the U.S. House of Representatives, rose to address the question of admitting Missouri as a free or slave state, his first attempt to speak on the subject after nearly a month of solid debate, right before the vote was to be called. To the exasperation of colleagues, he began a long and wearisome speech, explaining that he was speaking not to Congress but "to Buncombe."[1] He was ultimately shouted down by his colleagues,[2] though his speech was published in a Washington paper[3] and his persistence made "buncombe" (later respelled "bunkum") a synonym for meaningless political claptrap and later for any kind of nonsense,[1] at first only in the jargon of Washington and then in common usage (see discussion on talk page).[4]
From buncombe, from “speaking to (or for) Buncombe County, North Carolina”, a county in North Carolina named for Edward Buncombe. In 1820, Felix Walker, who represented the county in the U.S. House of Representatives, rose to address the question of admitting Missouri as a free or slave state, his first attempt to speak on the subject after nearly a month of solid debate, right before the vote was to be called. To the exasperation of colleagues, he began a long and wearisome speech, explaining that he was speaking not to Congress but "to Buncombe."[1] He was ultimately shouted down by his colleagues,[2] though his speech was published in a Washington paper[3] and his persistence made "buncombe" (later respelled "bunkum") a synonym for meaningless political claptrap and later for any kind of nonsense,[1] at first only in the jargon of Washington and then in common usage (see discussion on talk page).[4]