SAPONIN
saponin
(noun) any of various plant glucosides that form soapy lathers when mixed and agitated with water; used in detergents and foaming agents and emulsifiers
Source: WordNet® 3.1
Etymology
Noun
saponin (plural saponins)
(organic chemistry, steroid) Any of various steroid glycosides found in plant tissues that dissolve in water to give a soapy froth.
Source: Wiktionary
Sap"o*nin, n. Etym: [L. sapo, -onis soap: cf. F. saponine.] (Chem.)
Definition: A poisonous glucoside found in many plants, as in the root of
soapwort (Saponaria), in the bark of soap bark (Quillaia), etc. It is
extracted as a white amorphus powder, which occasions a soapy lather
in solution, and produces a local anæstesia. Formerly called also
struthiin, quilaiin, senegin, polygalic acid, etc. By extension, any
one of a group of related bodies of which saponin proper is the type.
Source: Webster’s Unabridged Dictionary 1913 Edition