Green’s Dictionary of Slang

giraffe n.¹

the swindle, the deception.

1844

M. Houstoun Texas (1845) 76: The latter, with the eternal quid in the corner of his mouth, is clearly looking out ‘for the giraffe’ [DA].

In phrases

come the giraffe (v.)

to hoodwink, to swindle.

1846		D. Corcoran Porfolio of the Reporter of the N.O. ‘Picayune’ 31: ‘No you don’t,’ said the watchman, ‘you don’t come the giraffe over me that a way, you is a great naturalist, and does like to see the elephant.’.
1867		R. Miller Pictorial Book of Anecdotes and Incidents of the War of the Rebellion 230: But she could not ‘come the giraffe’ over the Captain in that kind of style.
1914		in C.H. Henderson What it is to be Educated? 224: Don’t let them come the giraffe over you, my Boy.