born yesterday


born yesterday


  • naive; inexperienced
  • someone, like a new born baby with no experience
  • to be stupid or easy to mislead

The idiomatic expression is typically used in the negative, past-tense form as wasn’t born yesterday. As the negative use of this phrase is more prevalent, we’ve explained this expression with its negative meanings and examples to understand it clearly without any further confusion.

not born yesterday


  • not a completely naive person
  • well experienced person
  • when someone cannot easily be tricked
  • when someone is more experienced than they appear to be
  • someone who is not gullible

Example Sentences

  1. Susan might look young, but she was not born yesterday. She is not going to fall for your lies.
  2. My mom will never fall for it if I say that your parents are home. She was not born yesterday.
  3. I don’t believe that your dog ate your homework Pete. I was not born yesterday.
  4. “I am not paying that amount of money for a second-hand car! I was not born yesterday.”
  5. If you don’t know how to use the computer, then it’s as if you were born yesterday. (Positive Example.)
  6. He thought he can fool me, but I wasn’t born yesterday and I understand his tricks well.


The idiom became more widely used after the Broadway play Born Yesterday. It was based on a book by Garson Kanin. Both the Broadway play and subsequent movie starred Judy Holliday as a seemingly naïve blond who is far smarter than she is given credit for.

The phrase has been in use since the late 1800s but there is no definitive origin. The most obvious observation would be that with age comes wisdom. Thus, if someone was not born yesterday it means that they have been around for a while. This has given them ample opportunity to gain the necessary experience.

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Mark Twain’s beloved wife Livy died in 1904 and he started “translating” the diaries of Adam and Eve: another Biblical reference. Eve starts out by letting us know that she was born yesterday – if there had been an additional day, surely she would remember it. Great heartbreaking literature and I would bet playwright Kanin was familiar with Mark Twain. Time period fits as does the concept of an amazing new creature finding her way, relying on instinct rather than instruction.

‒ Old lady March 12, 2020

For we were born only yesterday and know nothing, and our days on earth are but a shadow. Job 8:9

‒ Tenshio February 10, 2019

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