An old person who is silly, senile, or excessively doting; a foolish aged person.
From 'dote' + '-ard' (suffix meaning 'one who does excessively,' as in 'drunkard'). 'Dottard' specifically implies excessive doting or senility.
The '-ard' suffix is used for people who do something excessively—'coward,' 'drunkard,' 'dullard'—so a 'dottard' is someone who takes doting to an extreme, usually with age as a factor.
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