Foul smelling; noxious (especially of gas/vapours)
Early 17th century: from late Latin mephiticus, from mephitis ‘noxious exhalation’.
“We were left, choking in a fog of mephitic gas.”
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