not know the first thing about somebody/something

not know the first thing about (someone or something)

To not know anything about someone or something. I don't know the first thing about computers, so you'll have to explain this to me really slowly. What's an attachment again? Geoff wouldn't know the first thing about how to take care of a baby. Thank goodness Frank is there to help babysit. Why do you presume to know what I would or wouldn't do? You don't know the first thing about me!
See also: first, know, not, thing
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

not know the first thing about someone or something

Fig. not to know anything about someone or something. I don't know the first thing about flying an airplane. She doesn't know the first thing about John.
See also: first, know, not, thing
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

not know the first thing aˈbout somebody/something

know nothing at all about somebody/something: I don’t know the first thing about Chinese history.
Farlex Partner Idioms Dictionary © Farlex 2017
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