I (OR SHE, ETC.) WASN'T BORN YESTERDAY
Meaning of I (OR SHE, ETC.) WASN'T BORN YESTERDAY in English
I ( or she, etc.) wasn't born yesterday
I am (or she, etc. is) not foolish or gullible.
→ born
Concise Oxford English vocab.
Сжатый оксфордский словарь английского языка.
2004