\Y*wis"\, adv. [OE. ywis, iwis, AS. gewis certain; akin to
D. gewis, G. gewiss, and E. wit to know. See {Wit} to know,
and {Y-}.]
Certainly; most likely; truly; probably. [Obs. or Archaic]
      ``Ywis,'' quod he, ``it is full dear, I say.''
                                               --Chaucer.
      She answered me, ``I-wisse, all their sport in the park
      is but a shadow to that pleasure that I find in
      Plato.''                                 --Ascham.
      A right good knight, and true of word ywis. --Spenser.
Note: The common form iwis was often written with the prefix
      apart from the rest of the word and capitalized, as, I
      wis, I wisse, etc. The prefix was mistaken for the
      pronoun, I and wis, wisse, for a form of the verb wit
      to know. See {Wis}, and cf. {Wit}, to know.
            Our ship, I wis, Shall be of another form than
            this.                              --Longfellow.