not born yesterday

Idioms  

1. More experienced and less naive than one appears to be, as in Don't think you can fool me; I wasn't born yesterday. This term gained currency from the title of Garson Kanin's popular Broadway play, Born Yesterday, which was made into an even more popular film. In both, Judy Holliday played a stereotypical dumb blonde who shows more common sense than her sophisticated acquaintances. [Early 1800s]

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Example Sentences

"You were not born yesterday, you understood exactly what you were doing," he said.

From BBC

Because he was not born yesterday, Engoron is unlikely to believe that being female is an all-purpose preventative from buying into gender stereotypes, however.

From Salon

I was not born yesterday, and the last few bogus trickle-down tax laws did not help me or anybody I know in any way.

From New York Times

Perhaps he was under the weather or had had a few cocktails but Kuttner was not born yesterday saw through his ploy. 

From Salon

“I was not born yesterday,” Renu says.

From New York Times