Forswore oneself is an idiomatic expression used to describe someone who has lied or broken a promise. There are several synonyms to this phrase, including perjured oneself, deceived, misled, betrayed, and reneged on one's word. When someone forswears themselves, it is often a conscious decision taken to deceive or mislead others. Other synonyms that can be used for this expression include disavowed, denied, repudiated, and recanted. In summary, the phrase forswore oneself is a powerful expression that describes how some people choose to act deceptively or untruthfully. It is important to always strive to remain truthful and honest to avoid the consequences of forswearing oneself.