Source : Webster's Revised Unabridged Dictionary (1913)

Dreg \Dreg\, n. [Prob. from Icel. dregg; akin to Sw. dr["a]gg,
   cf. Icel. & Sw. draga to draw. Cf. {Draw}.]
   Corrupt or defiling matter contained in a liquid, or
   precipitated from it; refuse; feculence; lees; grounds;
   sediment; hence, the vilest and most worthless part of
   anything; as, the dregs of society.

         We, the dregs and rubbish of mankind.    --Dryden.

   Note: Used formerly (rarely) in the singular, as by Spenser
         and Shakespeare, but now chiefly in the plural.

Source : WordNet®

dreg
     n : a small amount of residue