Green’s Dictionary of Slang

1. (also mud-grappler) a hand; thus grapplers, fingers.

1827		T. Morton A School For Grown Children IV iii: Get ready your grapplers.
1844		‘Jonathan Slick’ High Life in N.Y. II 212: I gin the chap a shove with one of my mud-grapplers. [Ibid.] 221: That other leetle hand in her lap kinder crept along [...] as if it wanted to get better acquainted with mine. My mud-grappler didn’t object to be introduced.
1852		H. Hazel Yankee Jack ii 9: ‘Give us your grappler on that, old fellow!’ said Paul, [...] seizing the merchant’s hand [OED].

2. a wrestler.

1966

Took & Feldman ‘Bona Grapplers’ Round the Horne [BBC radio] Jules and me have handled all the top grapplers at one time or another. Take the Hooded Terror – he’s one of ours. The Iron Man, he’s one too. Then there’s the Borneo maniac – comes on as a gorilla.