Sadism is a form of sexual gratification in which a person is sexually aroused and gratified by threat or infliction pain or humiliation and degradation on a more submissive sexual partner. This was first written about and described by the Marquis de Sade, which is where the word comes from.
Derived from the Marquis de Sade's name, it means to gain pleasure from hurting and humiliating others and was first introduced to the dictionary in 1834. The person on the receiving end of such treatment is, if willing, called a masochist. (See also Masochism.)