Source : Webster's Revised Unabridged Dictionary (1913)

Remercie \Re*mer"cie\, Remercy \Re*mer"cy\ (r[-e]-m[~e]r"s[y^]),
   v. t. [F. remercier; pref. re- re- + OF. mercier to thank,
   from OF. & F. merci. See {Mercy}.]
   To thank. [Obs.]

         She him remercied as the patron of her life. --Spenser.