The tomato is referred to as a "love apple" because its early scientific classification placed it in the category of a mandrake, which is considered an aphrodisiac with narcotic powers. This classification was a mistake, but the nickname has endured.
Tomatoes were misunderstood in Europe for several centuries. In the 1700s, it was believed that tomatoes were poisonous because some aristocrats had died after eating them. Later it was discovered that the acidic tomatoes had reacted with the pewter plates that were standard at that time, resulting in lethal lead poisoning. Tomatoes are a member of the nightshade family, which also includes eggplant.