Green’s Dictionary of Slang

1. in pl., handcuffs.

1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1830		J.B. Buckstone Wreck Ashore I iv: I hope the bailiffs have not laid their grappling irons on young Miles.
1845		D. Corcoran Pickings from N.O. Picayune (1847) 113: He is sure to lay his grappling irons on me and take me right off to the watchhouse.

2. (also grabbling irons) the hand; in pl., the fingers; the arms.

1844		Cork Examiner 14 June 2/6: Well you see, messmates, my chummy and I hailed her, when she immediately threw out her grappling irons, and lugged us along.
1851		G. Thompson Jack Harold 57: One Arm’d Bill [...] said [...] ‘although I’ve got no larnin’, and have lost one of my grappling-irons, I feel myself among pals and brothers’.
1852		Kendal Mercury 14 Feb. 3/3: Our grappling irons (hands) burnt like a lump of salt junk (beef).
1864, 1867, 1870		Hotten Sl. Dict.
1869		Man about Town 13 Nov. 79/3: [of a falcon’s talons] [H]is ‘grappling irons’ were a ‘caution’ — at least to me.
1895		Crowe Aus. Sl. Dict. 33: Grappling Irons, the hands.
1935		A.J. Pollock Und. Speaks.
1967		Current Sl. II:2 16: Grappling irons, n. Arms.

3. (US) in pl., spurs.

1922		P.A. Rollins Cowboy 116: Each spur, or ‘grappling iron,’ as slang often dubbed it, was kept in place [...] by a ‘spur-leather’.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: grappling irons. Spurs.