doesn't know beans

don't know beans

To know nothing or next to nothing. Don't ask me! I don't know beans about car engines.
See also: bean, know
Farlex Dictionary of Idioms.

doesn't know beans

Ignorance. The New England uncomplimentary description of a Bostonian who's so ignorant that he or she can't even cook the city's most famous dish of baked beans spread to the rest of the country.
See also: bean, know
Endangered Phrases by Steven D. Price
See also:
  • (I) can't say as I do(, can't say as I don't)
  • don't ask me
  • don't ask me!
  • all in (one's) head
  • come Monday
  • don't bet on it
  • don't give up the ship
  • don't cry before you are hurt
  • don't fret
  • don't give me that story
References in periodicals archive
She boldly decides to risk the little capital she has left to turn his farm into a grass-fed beef operation--never mind that she doesn't know beans about cattle.
The Carolina Connection
Yet, two years ago he got lucky on a big bull, and then, because he didn't have enough sense to know he doesn't know beans about writing, he wrote a story about that big bull--and we published it in Big Game Special 2002.
Getting started
The consulting team's magician justifies his position by stating he doesn't have any preconceptions, which usually means he doesn't know beans about the problem.
The rule of the realm