Green’s Dictionary of Slang

1. to commit oneself whole-heartedly, esp. to a fight.

1865		Leaves from Diary of Celebrated Burglar 110/2: We took the ‘brods’ to while away the time, as it was not convenient for Joe and I to ‘wade in’ with the other ‘spielers’ just then.
1872		S. Powers Afoot and Alone 130: We waded into ’em, and skinned ’em out mighty sudden [DA].
1883		Albany Echo 12 Dec. n.p.: Build a Chinese wall around Coleman County, put all the fence-cutters inside it, furnish them with wire fence and nippers, and tell them to wade in [DA].
1892		H. Lawson ‘The Man from Waterloo’ in Roderick (1967–9) I 220: The jackaroo made no remark / But peeled and waded in.
1900		Punch 28 Feb. 161/1: ‘Whether it’s a dog or a bear, you’ll just wade in at it,’ he said, severely, ‘same as if it was a bear.’.
1913		J. London Valley of the Moon (1914) 77: They’s times when [...] I wanted to jump over the ropes and wade into them, knock-down and drag-out, an’ show’m what fightin’ was.
1922		Joyce Ulysses 305: After a brisk exchange of courtesies [...] the lamb suddenly waded in all over his man and landed a terrific left to Battling Bennett’s stomach, flooring him flat.
1930		W.R. Burnett Iron Man 67: It took everybody in his corner to make him wade in.
1940		H. Drake-Brockman Hot Gold I iii: That Rienzi, he says Girlie wants t’ go with him. So I wades into him.
1960		Wodehouse Jeeves in the Offing 66: I wading into scrambled eggs.
1970		Sat. Rev. (US) 10 Oct. 20: When construction workers, some of them with crowbars, wade into a group of students, laying them about indiscriminately, not everyone joins in denouncing the hardhats.
1986		F. Taylor Auf Wiedersehen Pet Two 185: The rest of them waded into the champagne.
1998		K. Sampson Awaydays 43: The Busies are really wading in hard.
2001		I. Welsh Glue 85: Ah’d rather wade intae a mob ay Huns n take a bad panellin, thin shite it n huv tae face they radges ootside the school gates.

2. to begin eating or drinking.

1908

Sun. Times (Perth) 31 May 1/1: The fruit supplied at the South Western refreshment rooms is unfit for human food [...] the public are expected to wade manfully into windfalls.

3. to commence an action.

1915		Wodehouse Psmith Journalist (1993) 340: Be ready to wade in at a moment’s notice.
1924		C.J. Dennis ‘The Knight’s Return’ in Chisholm (1951) 86: Then ’e wades in an’ tells me ’oo ’e is – / (’e ain’t a bad ole coot when ’e ain’t shick).
2005		J. Stahl I, Fatty 83: Let me wade into it, though.