mid-15c. "swear falsely" (implied in perjured; late 13c. in Anglo-French), from Old French parjurer "to break one's word, renege on a promise" (11c.), from Latin periurare "to swear falsely, break one's oath" (see perjury). Reflexive sense is from 18c.[perjure etymology, perjure origin, 英语词源]