late 14c., name for the god of dreams in Ovid, son of Sleep, literally "the maker of shapes," from Greek morphē "form, shape, figure," especially "a fine figure, a beautiful form; beauty, fashion, outward appearance," a word of uncertain etymology. Related: Morphean. Morphō was an epithet of Aphrodite at Sparta, literally "shapely."

"chemical which occurs naturally in the brain and works like morphine," 1975, from French endorphine. First element from endogène "endogenous, growing within" (see endo- + genus); second element from morphine.

"morphine" in Latin form, 1818; see morphine.

"mad craving for morphine," 1885; see morphine + mania. Other words in the same sense were morphinism (1875, after German Morphiumsucht); morphiomania (1876). Related: Morphinomaniac; morphiomaniac.