odoriferous reddish-brown substance secreted by the male musk deer (dried and used in medicinal preparations and as a perfume), late 14c., from Old French musc (13c.) and directly from Medieval Latin muscus, from Late Greek moskhos, from Persian mushk, from Sanskrit muska-s "testicle," from mus "mouse" (so called, presumably, for resemblance; see muscle). The deer gland was thought to resemble a scrotum. German has Moschus, from a Medieval Latin form of the Late Greek word. Spanish has almizcle, from Arabic al misk "the musk," from Persian.
The musk-deer, the small ruminant of central Asia that produces the substance, is so called from 1680s. The name musk was applied to various plants and animals of similar smell, such as the Arctic musk-ox (1744). Musk-melon "the common melon" (1570s) probably originally was an oriental melon with a musky smell, the name transferred by error [OED]. Also compare Muscovy.