What is "a pig in a poke"

Pig \Pig\, n. [Cf. D. big, bigge, LG. bigge, also Dan. pige girl, Sw. piga, Icel. p[=i]ka.]

1. The young of swine, male or female; also, any swine; a hog. ``Two pigges in a poke.''
   --Chaucer.

2. (Zo["o]l.) Any wild species of the genus Sus and related genera.

3. [Cf. Sow a channel for melted iron.] An oblong mass of cast iron, lead, or other metal. See Mine pig, under Mine.

4. One who is hoggish; a greedy person. [Low]

   Masked pig. (Zo["o]l.) See under Masked.

   Pig bed (Founding), the bed of sand in which the iron from a smelting furnace is cast into pigs.

   Pig iron, cast iron in pigs, or oblong blocks or bars, as it comes from the smelting furnace. See Pig, 4.

   Pig yoke (Naut.), a nickname for a quadrant or sextant.

   A pig in a poke (that is, bag), a blind bargain; something bought or bargained for, without the quality or the value being known. [Colloq.]