Green’s Dictionary of Slang

to steal, usu. a horse; thus free a cat v., to steal a muff.

1839		H. Brandon Dict. of the Flash or Cant Lang. 163/1: To Free – to steal. To Free a Prad – to steal a horse.
1857		J. Archbold Magistrate’s Assistant (3rd edn) 444: To steal a muff – To free a cat.
1864, 1867, 1870		Hotten Sl. Dict.
1881		Trumble Sl. Dict. (1890).
1882		Sydney Sl. Dict. (2 edn) 4: Free - To steal. To Free a Prad - To steal a horse.