Source : Webster's Revised Unabridged Dictionary (1913)

Avouch \A*vouch"\, v. t. [imp. & p. p. {Avouched} (?); p. pr. &
   vb. n. {Avouching}.] [OF. avochier, LL. advocare to recognize
   the existence of a thing, to advocate, fr. L. advocare to
   call to; ad + vocare to call. Cf. {Avow} to declare,
   {Advocate}, and see {Vouch}, v. t.]
   1. To appeal to; to cite or claim as authority. [Obs.]

            They avouch many successions of authorities. --Coke.

   2. To maintain a just or true; to vouch for.

            We might be disposed to question its authenticity,
            it if were not avouched by the full evidence.
                                                  --Milman.

   3. To declare or assert positively and as matter of fact; to
      affirm openly.

            If this which he avouches does appear. --Shak.

            Such antiquities could have been avouched for the
            Irish.                                --Spenser.

   4. To acknowledge deliberately; to admit; to confess; to
      sanction.

            Thou hast avouched the Lord this day to be thy God.
                                                  --Deut. xxvi.
                                                  17.