early 15c., from Middle French ambre gris "gray amber" (see amber), "a wax-like substance of ashy colour, found floating in tropical seas, a morbid secretion from the intestines of the sperm-whale. Used in perfumery, and formerly in cookery" [OED]. King Charles II's favorite dish was said to be eggs and ambergris [Macauley, "History of England"]. French gris is from Frankish *gris or some other Germanic source (cf. Dutch grijs, Old High German gris; see gray).
Praise is like ambergris; a little whiff of it, by snatches, is very agreeable; but when a man holds a whole lump of it to his nose, it is a stink and strikes you down. [Pope, c.1720]
A yellow, gray, or black waxy material formed in the intestines of sperm whales that consists of a mixture of steroid derivatives. It is often found floating at sea or washed ashore, has a pleasant odor, and is added to perfumes as a fixative to slow down the rate of evaporation.