Chapter Youthful to Ywis of Y by Webster's Dictionary (1913 Edition)

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.