peanut

Where it comes from

Peanut ordinarily means the edible seed of a legume whose pods develop underground. Peanut is an English compound of pea and nut. Botanically, the plant belongs to the legume family with peas and beans, not to the botanical category of true nuts. Its seed tastes and is eaten like a culinary nut, while its pod develops underground after the fertilized ovary grows down into the soil.

How the meaning developed

The name therefore combines the plant's real legume kinship with the food category it resembles.

In use

A peanut is eaten like a nut, but its plant belongs to the legume family with peas and beans.
Its pods also develop underground.