не на простака напал

• НЕ НА ДУРАКА <ДУРУ, ПРОСТАКА> НАПАЛ highly coll

[sent; past only; fixed WO]

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⇒ you are (he is etc) underestimating the intelligence of the person with whom you are (he is etc) dealing (usu. used in contexts when the interlocutor underestimates the speaker's intelligence):

- I'm not the fool you take me for <he's not the fool you take him for etc>;

- what do you take me for (what do they take her for etc), a fool?;

- you (he etc) shouldn't take me (her etc) for a fool.

     ♦ "...Я камердинер молодого барина"... Но Лиза поглядела на него и засмеялась. "А лжёшь, - сказала она, - не на дуру напал. Вижу, что ты сам барин" (Пушкин 3). "I am the young master's valet."...But Lisa looked at him and laughed. "You're lying," she said. "I'm not the fool you take me for. I can see that you are the young master himself" (3b).