Word Origin & History
bunk (2)
"nonsense," 1900, short for bunkum, phonetic spelling of Buncombe, a county in North Carolina. During the protracted Missouri statehood debates, on Feb. 25, 1820, N.C. Representative Felix Walker began what promised to be a "long, dull, irrelevant speech," and he resisted calls to cut it short by saying he was bound to say something that could appear in the newspapers in the home district and prove he was on the job. "I shall not be speaking to the House," he confessed, "but to Buncombe." Bunkum has been Amer.Eng. slang for "nonsense" since 1847.
[buhngk] 
British Slang.