Forklore: Mad apple
Raw eggplant: yuck. Bitter, spongy, neither damp nor dry, a ghastly off-white color, dead-looking. The yuck factor might explain why ancient Indian doctors decided that eggplant was bad for you. This harmless vegetable, which originated in the Vietnam-Thailand area, picked up a bad rep in India, which didn't keep medieval people from eating it but did make them fear that it caused everything from cancer to warts.
In particular, they thought it caused insanity. That idea may be attributable to the Sanskrit word for eggplant, vatingana, which looks as if it means "something belonging to the wind class." In India, madness is called "the wind sickness," referring to the wayward, unpredictable thoughts of the insane.
When eggplant reached the Near East (vatingana having become badhinjan), the loony connotation followed it, although it ended up being the most popular vegetable there. The name became berenjena in Spanish, aubergine in French and melanzana in Italian ... and the Italians decided that melanzana was really mala insana, "mad apple."
Even today, when somebody contradicts himself in Egypt, a listener is likely to say, "Adi zaman al-bitingan" ("Uh-oh, here comes eggplant season").
-- Charles Perry