Old English thēaw ‘usage, custom’, (plural) ‘manner of behaving’, of unknown origin. The sense ‘good bodily proportions, muscular development’ arose in Middle English.
“He was more thew than thought if you know what I mean!”
“Memories aren’t known to be particularly veridical.”
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