What is "thieves' vinegar"

Vinegar \Vin"e*gar\, n. [OE. vinegre, F. vinaigre; vin wine (L. vinum) + aigre sour. See Wine, and Eager, a.]

1. A sour liquid used as a condiment, or as a preservative, and obtained by the spontaneous (acetous) fermentation, or by the artificial oxidation, of wine, cider, beer, or the like.

   Note: The characteristic sourness of vinegar is due to acetic acid, of which it contains from three to five per cent. Wine vinegar contains also tartaric acid, citric acid, etc.

2. Hence, anything sour; -- used also metaphorically.

   Here's the challenge: . . . I warrant there's vinegar and pepper in't.
   --Shak.

   Aromatic vinegar, strong acetic acid highly flavored with aromatic substances.

   Mother of vinegar. See 4th Mother.

   Radical vinegar, acetic acid.

   Thieves' vinegar. See under Thief.

   Vinegar eel (Zo["o]l.), a minute nematode worm ( Leptodera oxophila, or Anguillula acetiglutinis), commonly found in great numbers in vinegar, sour paste, and other fermenting vegetable substances; -- called also vinegar worm.

   Vinegar lamp (Chem.), a fanciful name of an apparatus designed to oxidize alcohol to acetic acid by means of platinum.

   Vinegar plant. See 4th Mother.

   Vinegar tree (Bot.), the stag-horn sumac ( Rhus typhina), whose acid berries have been used to intensify the sourness of vinegar.

   Wood vinegar. See under Wood.

Thief \Thief\ (th[=e]f), n.; pl. Thieves (th[=e]vz). [OE. thef, theef, AS. [thorn]e['o]f; akin to OFries. thiaf, OS. theof, thiof, D. dief, G. dieb, OHG. diob, Icel. [thorn]j[=o]fr, Sw. tjuf, Dan. tyv, Goth. [thorn]iufs, [thorn]iubs, and perhaps to Lith. tupeti to squat or crouch down. Cf. Theft.]

1. One who steals; one who commits theft or larceny. See Theft.

   There came a privy thief, men clepeth death.
   --Chaucer.

   Where thieves break through and steal.
   --Matt. vi. 19.

2. A waster in the snuff of a candle.
   --Bp. Hall.

   Thief catcher. Same as Thief taker.

   Thief leader, one who leads or takes away a thief.
   --L'Estrange.

   Thief taker, one whose business is to find and capture thieves and bring them to justice.

   Thief tube, a tube for withdrawing a sample of a liquid from a cask.

   Thieves' vinegar, a kind of aromatic vinegar for the sick room, taking its name from the story that thieves, by using it, were enabled to plunder, with impunity to health, in the great plague at London. [Eng.]

   Syn: Robber; pilferer.

   Usage: Thief, Robber. A thief takes our property by stealth; a robber attacks us openly, and strips us by main force.

   Take heed, have open eye, for thieves do foot by night.
   --Shak.

   Some roving robber calling to his fellows.
   --Milton.

n. (context UK archaic English) four thieves' vinegar.