Green’s Dictionary of Slang

1. (US campus) a ‘fast’ young man [? bummer n.³ ].

1855		Broadway Belle (NY) 1 Jan. n.p.: The ‘Ham Guard’ was founded by Captain Jack Appleton, the Bummer King [...] This fine company — formerly known as the ‘Bummer Cadets’ — continues with full ranks.
1863		Criminal Life (NY) 19 Dec. n.p.: We have the names of those bummers that hang around 17th street [...] every night .
1871		L.H. Bagg Four Years at Yale 43: Bum, a spree, society supper, or convivial entertainment of any sort, innocent or otherwise. Used also as a verb; whence is derived bummer, a fast young man, a fellow who bums. [Ibid.] 527: The number even of moderate ‘bummers’ – who perhaps ‘get tight’ once or twice a year, at the time of a society supper or some special celebration – is comparatively small.

2. (gay) a sodomite [bum n.¹ (1)].

1965		Guild Dict. Homosexual Terms 22: homosexual (n.): One with a sexual attraction for those of the same sex who practices sex exclusively with those of the same sex. Related terms: [...] bummer.
1972		B. Rodgers Queens’ Vernacular 17: The man who fucks in anal intercourse, as opposed to the one who is fucked [...] bummer (Brit).
1989		J. Morton Lowspeak.
2000		M. Manning Get Your Cock Out 57: I’m a bummer, does it matter?