Ywar
Y•war´, a. [See Aware.] Aware; wary. [Obs.] "Be ywar, and his way shun." Piers Plowman.

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]
""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. 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. Z.