Green’s Dictionary of Slang

1. (also wido) an alert, aware or clever person, one who is ‘no fool’.

1843		Cork Examiner 15 Mar. 4/5: Resembling a pick-pocket and being remanded [...] till your friends can [...] prove you are not Flash jack, alias Bunkem, alias the Mizzler, alias Jockey Wide O, alias Slippery Joe [...] alias Conkey Dick.
1845		Bell’s Life in Sydney 11 Oct. 2/3: The dodges of some of the wido’s are quite amusing, as we see them daily sneaking out with their cattle mounted by professed jockies [...] each one of course endeavouring to elude the vigilance of the other.
1847		Bell’s Life in Sydney 20 Mar. 2/6: The ‘charleys’ retired [...] in the most gentlemanly manner, with three times three [i.e. cheers] from the wide-os.
1859		Hotten Dict. of Modern Sl. etc.
1870		Hotten Sl. Dict.

2. a minor villain, a ‘spiv’.

1935		(con. 1920s) McArthur & Long No Mean City 80: ‘Leave it tae me,’ he said loftily, ‘I’ll pey they Plantation wideoes (hooligans) for the smashing they gave ye.’.
1938		J. Curtis They Drive by Night 221: ‘Real wide boy’, I said. ‘Wideo, that’s what he is. Wide as Regent Street.’.
1993		I. Welsh Trainspotting 20: It’s this boy’s clothes that gie him away, marking him oot as wide-o extraordinaire.
2001		I. Welsh Glue 54: Dozo Doyle, the big master criminal in the scheme, the wideo Terry wants tae be like.
2009		T. Black Gutted 193: A cocky-looking wido fronted me. ‘Get in the car, Dury’.
2018		I. Welsh Dead Man’s Trousers 67: A radge or a wideo gien ye hassle.