The Collaborative International Dictionary of English v.0.48:

Tret \Tret\, obs.
   3d pers. sing. pres. of Tread, for treadeth. --Chaucer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tret \Tret\, n. [F. traite a drawing, trading, journey, tax on
   wares in transit, anything diminishing the value of coins,
   fr. OF. traire to draw, L. trahere. See Trait.] (Com.)
   An allowance to purchasers, for waste or refuse matter, of
   four pounds on every 104 pounds of suttle weight, or weight
   after the tare deducted. --M'Culloch.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

TRET, weights and measures. An allowance made for the water or dust that may
be mixed with any commodity. It differs from tare. (q.v.)