The Collaborative International Dictionary of English v.0.48:

Aby \A*by"\, Abye \A*bye"\, v. t. & i. [imp. & p. p. Abought.]
   [AS. [=a]bycgan to pay for; pref. [=a]- (cf. Goth. us-, Ger.
   er-, orig. meaning out) + bycgan to buy. See Buy, and cf.
   Abide.]
   1. To pay for; to suffer for; to atone for; to make amends
      for; to give satisfaction. [Obs.]

   Syn: expiate
        [1913 Webster]

              Lest to thy peril thou aby it dear. --Shak.
        [1913 Webster]

   2. To endure; to abide. [Obs.]
      [1913 Webster]

            But nought that wanteth rest can long aby.
                                                  --Spenser.
      [1913 Webster]

WordNet (r) 3.0 (2006):

abye
    v 1: make amends for; "expiate one's sins" [syn: expiate,
         aby, abye, atone]