Source : Webster's Revised Unabridged Dictionary (1913)

Hackney \Hack"ney\, n.; pl. {Hackneys}. [OE. haceney, hacenay;
   cf. F. haquen['e]e a pacing horse, an ambling nag, OF. also
   haquen['e]e, Sp. hacanea, OSp. facanea, D. hakkenei, also OF.
   haque horse, Sp. haca, OSp. faca; perh akin to E. hack to
   cut, and orig. meaning, a jolting horse. Cf. {Hack} a horse,
   {Nag}.]
   1. A horse for riding or driving; a nag; a pony. --Chaucer.

   2. A horse or pony kept for hire.

   3. A carriage kept for hire; a hack; a hackney coach.

   4. A hired drudge; a hireling; a prostitute.