1550s, "favored food or drink of the gods," from Latin ambrosia, from Greek ambrosia "food of the gods," fem. of ambrosios, probably literally "of the immortals," from a- "not" (see a-(3)) + mbrotos, related to mortos "mortal," from PIE *mer- "to die" (see mortal, adj.). Applied to certain herbs by Pliny and Dioscorides; used of various foods for mortals since 1680s (originally of fruit drinks); used figuratively for "anything delightful" by 1731.