Green’s Dictionary of Slang

1. (also crack, crack along) to move along at speed, to bustle about.

1836		T. Haliburton Clockmaker I 79: He must have cracked on near about as fast as them other geese, the British travellers.
1847		Illus. London News 31 July 74/2: The trio coming [...] as hard as they could crack.
1876		broadside ballad quoted in C.G.Leland Captain Jonas n.p.: [...] they may go or stand, I’m darned if I don’t crack on [F&H].
1888		‘Rolf Boldrewood’ Robbery Under Arms (1922) 177: We cracked on for the Hollow in the morning.
1901		Boy’s Own Paper 27 Apr. 467: I’ll crack on all the same, even if I should carry away a spar. [Ibid.] 468: Ain’t we cracking on a bit too merrily in a fog like this?
1947		D. Davin For the Rest of Our Lives 250: He came cracking along this morning as if he thought it was going to be a walk-over.
1959		G. Slatter Gun in My Hand 199: Come on, honey, let’s crack along.
1960		R.M. Muir Word for Word 221: ‘I’ll crack along,’ Harry said. ‘I don’t know where the time gets to, these days.’.

2. to load up, to ‘clap on’.

1864

Appleton Crescent (WI) 13 Aug. 1/2: We cracked on more steam [...] and made all preparations for a short chase.

3. to get on with one’s work.

1945		D. Bolster Roll On My Twelve 128: So crack on, me hearties, and don’t make Grandma laugh while she’s shaving!
1958		(con. 1940s) B. Behan Borstal Boy 355: Well, I’ll crack on.
1969		Sun. Times 5 Jan. 11: Big John with his immense experience had things under his personal control (‘Crack on lads!’ was a favourite Big John order).
1988		A. Payne ‘The Last Video Show’ in Minder [TV script] 43: I hear her saying ‘Crack on Arthur, crack on!’.
2000		J.J. Connolly Layer Cake 3: What’s called for is [...] a low profile so you can crack on uninterrupted.
2007		N. ‘Razor’ Smith Raiders 102: I [...] told them to crack on if they wanted to get nicked.