Green’s Dictionary of Slang

1. one who hits powerfully, esp. a boxer.

1871		Burnley Gaz. 12 Aug. 3/5: But even Bob once met his match — / His wife too wer’ a socker.
1923		H.C. Witwer Fighting Blood 101: Sweet Mamma, what a socker you turned out to be!
1930		M. West Babe Gordon (1934) 20: ‘What kind of a socker is he?’ ‘A middleweight.’.
1944		C.S. Montanye ‘Death with Music’ in Thrilling Detective Feb. 🌐 The Orient Athletic Club, where Silk’s sockers trained.

2. a thug, a lout.

1889		Dead Bird (Sydney) 28 Sept. 4/2: ‘Balmain Bill, the Socker,’ has been recently converted, and now cannot be induced to do a crook for anything less than a fin.
1890–1904		Farmer & Henley Sl. and Its Analogues.

3. a simpleton, a fool.

1772

Bridges Burlesque Homer (3rd edn) 4: The rabble then began to swear, / What the old socker said was fair.

4. a heavy blow.

1898

Illus. Bits Xmas No. 50 n.p.: Then Maudie gets the needle, and [...] ketches me a fair ole rousin’ socker on the jore [F&H].