Webster's Revised Unabridged Dictionary · 1913

Forsooth

Forsooth , adverb

[Anglo-Saxon forsōe; for, prep. + sōe sooth, truth. See For, prep., and Sooth.]

In truth; in fact; certainly; very well; -- formerly used as an expression of deference or respect, especially to woman; now used ironically or contemptuously.
A fit man, forsooth, to govern a realm! — Hayward
Our old English word forsooth has been changed for the French madam. — Guardian

Forsooth , transitive verb

To address respectfully with the term forsooth. [Obsolete]
The captain of the “Charles” had forsoothed her, though he knew her well enough and she him. — Pepys

Forsooth , noun

A person who used forsooth much; a very ceremonious and deferential person. [Rare]
You sip so like a forsooth of the city. — B. Jonson