'benumb' originates from Middle English, specifically the combination of the prefix 'be-' (from Old English 'be-') and the adjective 'numb' (Old English 'numb'), where the prefix 'be-' meant 'about, thoroughly' and 'numb' meant 'without feeling; numbed'.

'benumb' changed from Middle English formations such as 'benummen' (a verb built with the prefix 'be-' plus 'numb') and eventually became the modern English verb 'benumb'.

Initially it meant 'to make numb' in a physical sense (for example by cold); over time it has retained that core meaning but also developed figurative uses meaning 'to dull emotional or mental responsiveness'.