not know beans

Idioms  

1. Also, not know the first thing; not know from nothing. Be ignorant about something, as in a poem published in the Yale Literary Magazine in 1855: “When our recent Tutor is heard to speak, This truth one certainly gleans, Whatever he knows of Euclid and Greek, In Latin he don't know beans.” The beans in this colloquial phrase, dating from the early 1800s, signify something small and worthless; not knowing the first thing about something clearly shows one doesn't know anything about it at all; and the third slangy phrase, with its double negative, implies stupidity as well as ignorance, as in Poor girl, just starting out and she doesn't know from nothing.

---

Example Sentences

Virginia Westmoreland St. Louis Psychologist Hazleton's protracted "dolor" may have qualified her as an expert on the blues, but about depression she does not know beans.

From Time Magazine Archive

She had never seen celery in trenches, she said, and would not know beans from gourds if she saw them growing.

From Project Gutenberg