[Wikipedia] Etymology, Use as Soap: The scientific name Saponaria is derived from the Latin sapo (stem sapon-) meaning "soap", which, like its common name, refers to its utility in cleaning. From this same Latin word is derived the name of the toxic substance saponin, contained in the roots at levels up to 20 percent when the plant is flowering [5] (Indian soapnuts contain only 15 percent). It produces a lather when in contact with water. (link added by Mary Ann Machi)
Calflora:
Information on California plants for education, research and conservation,
with data contributed by
public and private institutions and individuals.
[web application]. 2025.The Calflora Database
[a non-profit organization].Available:
https://www.calflora.org/(Accessed: 03/28/2025).