The Collaborative International Dictionary of English v.0.48:

Frett \Frett\, n. [See 2d Fret.] (Mining)
   The worn side of the bank of a river. See 4th Fret, n., 4.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Frett \Frett\, n. [See Frit.]
   A vitreous compound, used by potters in glazing, consisting
   of lime, silica, borax, lead, and soda.
   [1913 Webster]