In legend a potion is a concoction used to heal, bewitch or poison people, made by a magician, sorcerer or witch. i.e., there can be cited love potions, intended to make a person fall in love with other, or potions for the opposite effect, intending that a person hate another.
During the 19th Century it was common in certain countries to see wandering charlatans offering potions to heal every disease, ache, etc. In later years, these became replaced by/known as patent medicines.