Green’s Dictionary of Slang

(US) excellent, first-rate, esp. of food; thus the real bunkum, something first-rate.

1834		Military and Naval Mag. of US May 203: ‘Oh, I’m bunkum,’ replied Dave. ‘I never enjoyed myself more.’ [HDAS].
1836		Knickerbocker (N.Y.) VII 19: ‘Ain’t she [i.e. a boat] the raal bunkum?’ exclaimed Hal [DAE].
1849		Knickerbocker (N.Y.) Nov. 407/1: Ye see, the Yankees say a thing’s ‘bunkum’ when it’s good enuff as it is; the Canada Frenchers say ‘Bunq cum sa’ [DA].
1854		‘Derby Ram’ in C. Elliot Songs of Yale (1870) 75: When I get into business, / And count my numerous boys, / I’ll send them to old Yale, sir, / To taste her bunkum joys.
1880		Harper’s Mag. XLI 615/1: I had heard the word ‘bunkum’ often used by bumpkins, but always with reference to something of an edible character, as an apple being ‘bunkum,’ or a piece of cake or pie [DA].
1905		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:i 72: bunkum, adj. Excellent.
1910		‘Word-List From West Brattleboro’ in DN III:vi 452: bunkum, adj. 1, Sturdy, strong. ‘That wagon isn’t very bunkum.’ 2. In good health. ‘How are you?’ ‘I’m pretty bunkum.’.
1913		E.L. Warnock ‘Terms of Approbation And Eulogy’ in DN IV:i 24: bunkum. Fine, first-class. [...] ‘Their supper was just bunkum.’.