'blockhead' originates from English, formed by combining the words 'block' and 'head', where 'block' originally meant 'a piece of wood' and 'head' meant 'head'.

'block' came into English from Middle Dutch or Middle Low German 'block' meaning 'log' or 'chunk of wood', while 'head' comes from Old English 'heafod'. The compound 'blockhead' arose in Early Modern English as a figurative insult (literally 'wooden-headed').

Initially it conveyed the image of a 'head like a block' (thick or insensitive), and over time it evolved into the familiar modern sense of 'a stupid person'.