From the Latin genius, meaning a guardian deity or spirit. Today this is often equated with the Arabic term Jinni, although they traditionally have a different root and meaning. See also Jinni.
Readers, please enjoy this guest blog post by Sandra Kynes, author of several books, including The Herb Gardener's Essential Guide, Plant Magic, and the new Witches' Encyclopedia of Magical Plants, among many others.
Although a few old books...