Source : Webster's Revised Unabridged Dictionary (1913)

Aye \Aye\, Ay \Ay\, adv. [Icel. ei, ey; akin to AS. [=a],
   [=a]wa, always, Goth. aiws an age, Icel. [ae]fi, OHG, ?wa, L.
   aevum, Gr. ? an age, ?, ?, ever, always, G. je, Skr. ?va
   course. ?,?. Cf. {Age}, v., {Either}, a., {Or}, conj.]
   Always; ever; continually; for an indefinite time.

         For his mercies aye endure.              --Milton.

   {For aye}, {always}; forever; eternally.