Containing soap; soapy.
Early 18th century: from modern Latin saponaceus (from Latin sapo, sapon- ‘soap’) + -ous.
“It has saponaceous roots; the natives use it all the time.”
The last stage of life; old age.
Senectitude comes from the Medieval Latin noun senectitūdō meaning “old age,” which in turn comes from Classical Latin senectūs, a derivative of the noun senex meaning “old man.” Senectitude entered English in the late 1700s, more precisely, in 1796 in Jonathan Swift’s Gulliver’s Travels