1
general::
Phrase(s): swear by someone or something
1. Lit. to utter an oath on someone or something. • I swear by Jupiter that I will be there on time. • She swore by her sainted mother that she would never do it again. • The sheriff swore by his badge that he would lock her up if she ever did it again. 2. Fig. to announce one’s full faith and trust in someone or something. • I would swear by Roger any time. He is a great guy, and he tells the truth. • I swear by this computer. It has always served me well.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
1. Have great reliance on or confidence in, as in She swears by her personal physician. [Early 1800s] 2. Also, swear to. Have reliable knowledge of, be sure of, as in I think she was going to the library but I can't swear to it. [Mid1700s] 3. Take an oath by, as in I swear by all the saints in heaven. [Early 1200s]
American Heritage Idioms