'dotage' originates from Middle English, formed from the verb 'dote' plus the nominal suffix '-age'. The verb 'dote' meant 'to be foolish or to act like a fool.'

'dote' appears in Middle English as 'doten' (from earlier Old English or related Germanic roots meaning 'be foolish'); the noun 'dotage' was formed by adding the suffix '-age' in Middle English and carried into modern English with similar form.

Initially it meant 'a state of being foolish or weak-minded'; over time this core meaning has largely remained, though a secondary sense of 'foolish fondness' developed and is used more in literary or archaic contexts.