Source : Webster's Revised Unabridged Dictionary (1913)

Certes \Cer"tes\, adv. [F. certes, for [`a] certes, fr. L.
   certus. See {Certain}.]
   Certainly; in truth; verily. [Archaic]

         Certes it great pity was to see Him his nobility so
         foul deface.                             --Spenser.