'baldpate' originates as a compound of the adjective 'bald' and the noun 'pate' in English; 'bald' comes from Old English (e.g. 'bald', 'beald') and 'pate' comes via Middle English from Old French 'patene' meaning 'pan' and later 'head'.

'bald pate' (two words) in Early Modern English and earlier was used literally for a 'bald head'; over time the two-word phrase was sometimes written together as 'baldpate' and used figuratively to mean a foolish person; the plural form became 'baldpates'.

Initially it meant 'a bald head' (literal); over time it also came to be used figuratively for 'a dull or foolish person', a usage that is now somewhat old-fashioned or humorous.