The Collaborative International Dictionary of English v.0.48:

thave \thave\ (th[=a]v), n.
   Same as theave. [Prov. Eng.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Theave \Theave\, n. [Cf. W. dafad a sheep, ewe.]
   A ewe lamb of the first year; also, a sheep three years old.
   [Written also thave.] [Prov. Eng.] --Halliwell.
   [1913 Webster]