not know the first thing about

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, thing

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not know the first thing about something (spoken)

to know nothing about something not know beans about something I don't know why you're asking Alice, she doesn't know the first thing about sports.

See also: first, know, thing