Musk is the name originally given to a substance with a penetrating oor obtained from a gland of the male musk deer, which is situated between its stomach and genitals. The substance has been used as a popular perfume fixative since ancient times and is one of the most expensive animal products in the world. The name, originated from Sanskrit muṣká meaning "testicle" (as in a 'single' testicle), has come to encompass a wide variety of substances with somewhat similar odors although many of them are quite different in their chemical structures. They include glandular secretions from animals other than the musk deer, numerous plants emitting similar fragrances, and artificial substances with similar odors.