Green’s Dictionary of Slang

(US/S.Afr.) a legless person, usu. a beggar.

1918		‘A-No. 1’ Mother of the Hoboes 43: The Rating Of The Tramps. 20 Halfy: train rider who losts [sic] both legs above knee.
1923		N. Anderson Hobo 101: [From A No. 1, The Famous Tramp] 20. Halfy. Train rider who lost both legs below knee.
1931		Irwin Amer. Tramp and Und. Sl. 95: Halfy. – A beggar with both legs off at the hips; any legless individual; a half a man.
1947		N. Algren Neon Wilderness (1986) 135: He [...] asked himself what harm, after all, a halfy on a box could do to an able-bodied grammar-school graduate like himself.
1960		P. Oliver Blues Fell this Morning 113: With the characteristic combination of pithiness and pitilessness that labels a legless man as ‘Halfy’.
1963		L.F. Freed Crime in S. Afr. 106: A ‘halfy’ is a legless cripple.