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It's true, whether or not you agree, as in Believe it or not, I finally finished painting the house. Originating in the 1800s, this phrase gained currency as the title of a cartoon series begun in 1918 by Robert Ripley and continuing to run in American newspapers long after his death in 1949. Each drawing presented a strange but supposedly true phenomenon, such as a two-headed chicken.
American Heritage Idioms
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Phrase(s): believe it or not
(you may) choose to accept something as true or not; it may seem amazing but it’s true. • It’s late, but believe it or not, I just got home from work. • I’m over fifty years old, believe it or not.
McGrawhill's American Idioms And Phrasal Verbs