豆 first drew something no farmer ate: a tall ceremonial dish on a stem, used three thousand years ago to serve meat and grain to ancestors at sacrifice. The word for that vessel just happened to sound like the word for the little round bean people also had on the table, so scribes borrowed the same drawing for both — and over the centuries the bean meaning won out completely.
A piece of culture
The bean that became tofu Soybeans (大豆, "big bean") have been grown in China for at least three thousand years, and legend credits a Han-dynasty prince, Liu An, with discovering tofu around 164 BCE while experimenting with alchemy. Whether the story is exactly true or not, tofu (豆腐, "bean curd") spread from China across East Asia and is now eaten worldwide — a humble bean turned into one of the great plant proteins of world cuisine.
Use it in a real word
土豆
tǔdòu · tou2 dau6
potato — literally "earth bean"; you already know 土