Forswear, v. t. [imp. Forswore; p. p. Forsworn; p. pr. & vb. n. Forswearing.]
Etymology: [OE. forsweren, forswerien, AS. forswerian; pref. for- + swerian to swear. See For-, and Swear, v. i.]
1. To reject or renounce upon oath; hence, to renounce earnestly, determinedly, or with protestations. I . . . do forswear her. Shak.
2. To deny upon oath. Like innocence, and as serenely bold As truth, how loudly he forswears thy gold! Dryden. To forswear one's self, to swear falsely; to peforswear thyself."
Syn. -- See Perjure.
1 other Webster entry under this spelling
Forswear, v. i.
To swear falsely; to commit perjury. Shak.
Shades of meaning
Fernald has no entry of its own for forswear; he lists it under abandon, renounce.
Where he writes about it:
Abjure, discard, forswear, recall, recant, renounce, retract, and revoke, like abandon, imply some previous connection. — from renounce
Abjure (L. ab, away, and juro, swear) is etymologically the exact equivalent of the Saxon forswear, signifying to put away formally and under oath, as an error, heresy, or evil practise, or a condemned and detested person. — from renounce