Ywis \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] [1913 Webster] ``Ywis,'' quod he, ``it is full dear, I say.'' --Chaucer. [1913 Webster] She answered me, ``I-wisse, all their sport in the park is but a shadow to that pleasure that I find in Plato.'' --Ascham. [1913 Webster] A right good knight, and true of word ywis. --Spenser. [1913 Webster] 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. [1913 Webster] Our ship, I wis, Shall be of another form than this. --Longfellow. [1913 Webster]