'distend' originates from Latin, specifically the word 'distendere', where 'dis-' meant 'apart' and 'tendere' meant 'to stretch'.

'distend' changed from Latin 'distendere' (and Medieval Latin/Old French forms such as 'distendre') into Middle English (e.g. 'distenden') and eventually became the modern English 'distend'.

Initially, it meant 'to stretch apart' in a literal sense; over time it came to be used especially for 'to swell or expand (often from internal pressure)', the dominant modern sense.