Green’s Dictionary of Slang

1. to recognize; to understand.

1850		Cork Examiner 6 Feb. 4/3: I took to screeving (writing on the stones) [...] I did very well at first [...] till I got grannied.
1859		Hotten Dict. of Modern Sl. etc. 47: ‘Do ye granny the bloke?’ do you know the man.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 312/1: The ‘swells’ [...] ‘come down with a couter’ (sovereign) if they ‘granny the mauley’ (perceive the signature) of a brother officer or friend. [Ibid.] 415/2: The Shallow got so grannied (known) in London, that the supplies got queer, and I quitted the land navy.
1873		Sl. Dict.
1881		Newcastle Courant 2 Dec. 6/6: ‘Did yer see him wot has just gone past, Joe?’ ‘Yes, it’s the Nobbler, and we’ll have to keep our peepers open or he’ll nobble us.’ ‘Do yer think he grannied us?’.
1891		F.W. Carew Autobiog. of a Gipsey 409: Square indeed! I’ll square the chatty flymps [...] I’ll precious quick make ’em granny who’s omee here.
1935		A.J. Pollock Und. Speaks 31/1: Did they granny you? Did they recognize you (police show-up).

2. (UK Und.) to survey, to look over (prior to a robbery).

1865

Leaves from Diary of Celebrated Burglar 9/1: So next day we spent in ‘grannying’ the ‘drum’ and fixing upon the best mode of entrance.