Green’s Dictionary of Slang

(a) a fight.

1865		Leaves from Diary of Celebrated Burglar 5: Such meetings don’t always end as they begin, it being customary to wind up with a general ‘slog’ or at least a private ‘scrapp’.
1866		Wild Boys of London I 7/1: He ain’t much in a slog; but he can put the hug on to rights; and in they goes, right and left.
1888		Hants Teleg. 29 Sept. 11/6: He calls a man a ‘Johnny,’ a battle ‘a blooming slog’.

(b) a blow (with a blackjack or cosh).

1865

Leaves from Diary of Celebrated Burglar 81/1: Joe drew his ‘neddy’ ready for the ‘slog’.

(a) work that is definitely hard and poss. unrewarding.

1888		C.T. Jacobi Printers’ Vocab. 127: When a person is working hurriedly he is said to have a ‘slog on’ [OED].
1903		A. McNeill Egregious Eng. 172: That one way amounts to sheer mechanism and slog [OED].
1975		‘P.B. Yuill’ Hazell and the Three-card Trick (1977) 15: Two months’ solid slog in every department, and a seat on the board as a reward.
1981		S. Berkoff Decadence in Decadence and Other Plays (1985) 35: When we’re not too tired from slog / hustling down the highest.
1999		Indep. Education 15 July 4: The success and hard slog of all our teachers.
2000		Indep. on Sun. Real Life 16 Jan. 9: It’s not like the usual slog in the gym.
2024		D. Swierczynski California Bear 7: The day was a slog, and she spent most of it worried about her final English paper.

(b) an exhausting journey, usu. on foot.

1986		R.G. Barrett Godson 153: ‘[W]e ought to [...] take that trail [...] up round that ridge. Might be a bit of a slog, but it won’t do us any harm’.
1997		L. Davies Candy 25: We’ll follow this track along the creek for [...] about fourteen Ks. That’ll be quite a slog.
2001		A. Sillitoe Birthday 59: It used to be a real slog on the push-bike.