The Collaborative International Dictionary of English v.0.48:

Thwaite \Thwaite\, n. (Zool.)
   The twaite.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thwaite \Thwaite\, n. [CF. Icel. [thorn]veit a piece of land,
   fr. [thorn]v[imac]ta to cut. See Thwite, and cf. Doit,
   and Twaite land cleared of woods.]
   Forest land cleared, and converted to tillage; an assart.
   [Obs. or Prov. Eng.]
   [1913 Webster]

   Note: Thwaite occurs in composition as the last element in
         many names of places in the north of England; as, in
         Rosthwaite, Stonethwaite.
         [1913 Webster]