Green’s Dictionary of Slang

to denigrate.

c.1786		Johnson in Piozzi Anecdotes of the Late Jamuel Johnson 37: ‘’Tis pity,’ said I laughing, ‘that he had not heard you compliment the Cambridge men after dinner to-day.’ ‘Why (replied he) I was inclined to down them sure enough’.
1890		Sporting Times 1 Feb. 2/1: I had half packed up a nice, dirty, comfortable, worn-out old brown suit, when that was downed on by the Oracle.
1902		S.E. White Blazed Trail 185: Can’t down the Old Fellow.
1922		Ethel Waters ‘Kind Lovin’ Blues’ 🎵 Some people doubt me, most talk about me just to down my name.
1926		S. O’Casey Plough and the Stars Act II: Swingin’ heavy words about he doesn’t know th’ meanin’ of, and uppishly thryin’ to down a man like Mister Fluther here.
1934		A. Halper Foundry 54: He was not to be downed so easily.
1941		K. Tennant Battlers 118: People were trying to ‘down’ her. [...] As soon as you came near people who had houses or shops or businesses, they looked at you as though you ought to fade off the earth. They made you feel small and not worth the money.
1964		R. Abrahams Deep Down In The Jungle 152: He said, ‘Mr. Lion, the way he talking ’bout your mother, down your cousins.’.
1967		K. Tennant Tell Morning This 394: ‘A man’s [...] gotta jump right in with both feet when someone downs one of his own side’.
1971		R.D. Pharr S.R.O. (1998) 56: One of those chicks who never feel secure unless they’re downing somebody who’s already made it.
1977		in K. Gilbert Living Black 100: I won’t down him.
1982		P. Bailey An Eng. Madam 36: My father had downed me all my life. I honestly thought that I was nothing.
1997		Simon & Burns Corner (1998) 272: She’s always downing me that way [...] talking about what he should be doin’ and how he should be livin’.
2001		C. Amende Crossword Obsession 19: She [...] mailed me a manila envelope with letters of praise for a novel idea—and just as many downing it, saying that it was not a true puzzle.