I don't know beans about investing.
Castor bean tree.
Not to know beans about something.
- Energetic; frisky:.The children were too full of beans to sit still.
- Badly mistaken:.Don't believe him; he's full of beans.
- To disclose a secret.
- Full of energy and vitality; lively.
- Mistaken; in error.
- To divulge secret information.
Origin of bean
- Middle English ben broad bean from Old English bēan bha-bhā- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
- From Middle English bene, from Old English bēan (“bean, pea, legume”), from Proto-Germanic *baunō (“bean”), from Proto-Indo-European *bʰabʰ- (“bean”). Cognate with Scots bene, bein (“bean”), West Frisian bean (“bean”), Dutch boon (“bean”), German Bohne (“bean”), Danish bønne (“bean”), Icelandic baun (“bean”), Latin faba (“bean”), Russian боб (bob, “bean”).