"sleeping berth," 1758, probably a shortened form of bunker (n.) in its sense "seat." Bunk-bed (n.) attested by 1869.
"nonsense," 1900, short for bunkum, phonetic spelling of Buncombe, a county in North Carolina. The usual story (by 1841) of its origin is this: At the close of the protracted Missouri statehood debates, supposedly on Feb. 25, 1820, N.C. Representative Felix Walker (1753-1828) 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 American English slang for "nonsense" since 1841 (from 1838 as generic for "a U.S. Representative's home district").
MR. WALKER, of North Carolina, rose then to address the Committee on the question [of Missouri statehood]; but the question was called for so clamorously and so perseveringly that Mr. W. could proceed no farther than to move that the committee rise. [Annals of Congress, House of Representatives, 16th Congress, 1st Session, p. 1539]
"to sleep in a bunk," 1840, originally nautical, from bunk (n.1). Related: Bunked; bunking.
To cheat; defraud; bunco: couldn't possibly have done a better job of bunking the American people (1870s+)
[fr the explanation by a 1800s politician that his extraordinary statements were meant only for his constituents in Buncombe County, North Carolina]