Characterised by shrewdness. Shrewd.
Late 16th century: from Latin argutus ‘made clear, proved, accused’
“His argute summary made it clear what the problem was.”
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