What's the "een" in Halloween?
1892, in cookery sense, from French mousse, from Old French mousse "froth, scum," from Late Latin mulsa "mead," from Latin mulsum "honey wine, mead," from neuter of mulsus "mixed with honey," related to mel "honey" (see Melissa). Meaning "preparation for hair" is from 1977. As a verb in this sense from 1984.
savoury or sweet dish with the consistency of a dense foam, composed of a pureed chief ingredient mixed with stiffly beaten egg whites, whipped cream, or both. Mousses are almost always cold dishes, sweet mousses sometimes being served frozen. Savoury mousses are frequently prepared from poultry, foie gras, fish, or shellfish, to be eaten as a first course or light entree. They may be stabilized by the addition of gelatin.