Aver /(ā"vẽr)/

1. A work horse, or working ox. [Obs. or Dial. Eng.]

imp. & p. p. Averred; p. pr. & vb. n. Averring

1. To assert, or prove, the truth of. [Obs.]
2. To avouch or verify; to offer to verify; to prove or justify. See Averment. (Law)
3. To affirm with confidence; to declare in a positive manner, as in confidence of asserting the truth.

   It is sufficient that the very fact hath its foundation in truth, as I do seriously aver is the case.

   Then all averred I had killed the bird.