Green’s Dictionary of Slang

badly, incompetently.

1883		Atchison (KS) Globe 17 Nov. 8/8: Of course Mr. M brought in some new show slang; in speaking of Fay Templeton’s company in Omaha, he said, ‘They acted very bum’.
1890		Chillicothe (MO) Constitution 7 Oct. 4/2: Australians [...] are enriching the language with plenty of slang phrases. When a thing is moribund in Australia, they say colloquially, ‘It is going bum’.
1941		N.Y. Age 10 May 9/6: Mow, don’t you Unhips feel too blue, I too once wrote as bum as you.