I Wasn't Born Yesterday spoken language informal
You think you got me but it was not that easy. I wasn't born yesterday.
That was the most ridiculous story I've ever heard. I wasn't born yesterday.
To have no money
Used to describe someone who is naive, gullible, inexperienced, easily fooled, ignorant, unsophisticated, etc.
To say, or believe something or someone that seems completely crazy, delusional, or stupid
A person who is low-witted or stupid
To be extremely stupid; not to be alert
The idiom has been used since the late 1800s but the exact origin couldn't be confirmed. The idiom was used widely after the Broadway play Born Yesterday, which was based on a book by Garson Kanin.
White lie
Ken: Yesterday I lost the watch that my girlfriend presented to me. Should I tell her this thing?
Lily: Certainly Not! Your girlfriend will be angry with you. Children and fools tell the truth.