dotard
An old person with impaired intellect; a senile person; one in their dotage.
archaic
Seemes that through many yeares thy wits thee faile, And that weake eld hath left thee nothing wiſe, Els neuer ſhould thy iudgement be ſo frayle, To meaſure manhood by the ſword or mayle.
Dotard, (ſaide he) let be thy deepe aduiſe;One who dotes on another, showing excessive fondness; a doter.
obsolete
Where it comes from
From Middle English dotard; equivalent to dote + -ard.
Adapted from the Wiktionary entry dotard (CC BY-SA 4.0).