Green’s Dictionary of Slang

1. to esteem, to value; usu. as a negative.

1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 411/1: I don’t reckon that prison. Every time I came out harder than I went in.
1882		Dundee Courier (Scot.) 8 Sept. 7/3: I was ‘reckoning up’ the ‘stingy hole of a town’.
1899–1900		H. Lawson ‘The Babies in the Bush’ in Roderick (1972) 403: He was reckoned a mean ‘boss’, and rather a nigger-driver.
1905		‘Doss Chiderdoss’ ‘Scenic’ Sporting Times 11 Feb. 1/4: They were mummers [...] / And, discussing that night’s new production, they, / While imbibing moist refreshment in a private bar apart, / Reckoned up the ‘show’ just in the old sweet way.
1958		F. Norman in Bristol Eve. Post 27 Nov. in Norman’s London (1969) 42: They found me a job on a nursery [...] but I didn’t reckon this job nothing.
1962		F. Norman Guntz 77: I didn’t reckon him all that much.
1979		F. Norman Too Many Crooks Spoil the Caper 16: I don’t reckon it when geezers start larkin’ about on my manor unless I know wot’s buzzin’.
1993		I. Welsh Trainspotting 22: You reckon these then, man?
2001		K. Waterhouse Soho 25: Went there one time with summer the lads, that’s all. Didn’t reckon it.

2. to know, to be aware of.

1862		J.A. Hardwick ‘The London Scamp’ in Prince of Wales’ Own Song Book 50: Living reckless, gay, and free, [...] Reckoning up society / Like a wido London scamp – A regular downy London scamp.
1995		J. Cameron Vinnie Got Blown Away 4: You reckon my mate Vinnie?
1999		J. Cameron Brown Bread in Wengen [ebook] ‘Noreen straight up I never reckoned the geezer. Fuck knows what he was after’.