Green’s Dictionary of Slang

1. (US Und.) of a confidence man, to gain a victim’s trust and thus lure him deeper into the ‘game’; cite 1855 ref. to a brothel.

1855		Life in Boston & N.Y. (Boston, MA) 14 Apr. n.p.: Kate Wise’s nigger help are in the habit of ‘picking up’ white men and ‘roping’ them into her domicil.
1863		‘Paddy Burke’ Donnybrook-Fair Comic Songster 66: May the Peter Funks rope ’em, / And John Anderson smoke ’em.
1873		J. O’Connor Wanderings of a Vagabond 203: In the meantime [he] obtained an insight into the immense profits to be derived from roping suckers to brace games.
1894		Truth (Sydney) 30 Sept. 4/6: For all the ‘roping’ and ‘stiffening’ of potential frauds [that] took place.
1906		Cameron Co. Press (PA) 29 Mar. 6/3: The latter was to ‘rope’ Biebush [...] the wary Biebush at last being drawn into the net .
1929		Hostetter & Beesley It’s a Racket! 236: rope — To gain one’s confidence and get information.
1938		H. Asbury Sucker’s Progress 271: Another who sometimes roped for the Elite was George W. Post, a notorious confidence man.
1940		D. Maurer Big Con 4: Steering him to meet the insideman. (Roping the mark.).
1951		D. Dressler Parole Chief 235: This part of the procedure is called ‘roping the mark.’.
1961		J. Scarne Complete Guide to Gambling.
1968		(con. c.1900) J. Thompson King Blood (1989) 25: She tipped the ‘fool’ she had roped, and the fool hollered copper.

2. (Aus.) in weak use of sense 1, to attract, to interest.

1880

Bulletin (Sydney) 9 Oct. 2/2: Our picture posters have ‘roped’ my sympathies once again.

3. (US und.) by ext. of sense 1, to gain the confidence of a criminal.

1894		Worthington Advance (MN) 31 May 6/2: The ordinary detective does more ‘roping’ and ‘shadowing’ than anything else.
1912		A. Train Courts, Criminals & the Camorra 114: In the case of a murderer, in a majority of cases, his capture is the result of skilful ‘roping’ by an astute detective who manages to get into his confidence.
1930		D. Hammett Maltese Falcon (1965) 305: ‘Well, what do you want? Talk turkey. Who in hell do you think you are, coming in here trying to rope me?’ .

4. (US und.) to spy on criminals.

1927

‘Jargon of the Und.’ in DN V 461: Rope, to spy upon criminals.