swear by

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 . [Mid-1700s]

3. Take an oath by, as in I swear by all the saints in heaven . [Early 1200s]

Example Sentences

All of these sports have their own history and methods; specific forms, procedures and even credos that those who take up the fight swear by.

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Tech moguls swear by it, Hollywood stars insist it keeps them trim.

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Lucy and Serena swear by them.

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So what about some of the other health targets that many of us swear by?

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There are home-burger hobbyists who swear by mixing in bacon lardons.

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