From The Collaborative International Dictionary of English v.0.48:
Dreg \Dreg\ (dr[e^]g), n. [Prob. from Icel. dregg; akin to Sw.
dr[aum]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.
[1913 Webster]
We, the dregs and rubbish of mankind. --Dryden.
[1913 Webster]
Note: Used formerly (rarely) in the singular, as by Spenser
and Shakespeare, but now chiefly in the plural.
[1913 Webster]