To swear a falsehood, lie under oath, commit perjury; refl. to perjure oneself; forsworen man, a forsworen, perjurer. …

(a) To utter an oath; make a solemn or ceremonial declaration with an appeal to a deity, sacred object, etc. in confirmation of what is said; also, in the name of an allegorical place [quot. c1400]……