mousse (n.)

1892, in cookery sense in reference to a frothy dish stiffened with egg whites, etc., 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" (from PIE root *melit- "honey"). Meaning "preparation for hair" is from 1977, so called for resemblance of the substance. As a verb in this sense from 1984. Related: Moussed.

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Definitions of mousse from WordNet
mousse (n.)
a rich, frothy, creamy dessert made with whipped egg whites and heavy cream;
mousse (n.)
a light creamy dish made from fish or meat and set with gelatin;
mousse (n.)
toiletry consisting of an aerosol foam used in hair styling;
Synonyms: hair mousse
mousse (v.)
apply a styling gel to;
she mousses her hair
Synonyms: gel