Green’s Dictionary of Slang

(orig. US Und.) a person lacking one or more fingers.

1918		‘A-No. 1’ Mother of the Hoboes 43: The Rating Of The Tramps. 14 Fingy or Fingers: train rider who lost one or more fingers.
1923		N. Anderson Hobo 100: [From A No. 1, The Famous Tramp] 14. Fingy or Fingers. Train rider who lost one or more fingers.
1931		Irwin Amer. Tramp and Und. Sl. 73: Fingy.–One who has lost one or more digits from the hand.
1949		Monteleone Criminal Sl. (rev. edn).
1997–2000		Da Bomb 🌐 10: Fingy: A person with a finger or two missing.