'unintended' originates from the prefix 'un-' meaning 'not' and the verb 'intend' from Latin 'intendere', where 'in-' meant 'toward' and 'tendere' meant 'to stretch'.

'intendere' transformed into the Old French word 'entendre', and eventually became the modern English word 'intend'. The prefix 'un-' was added to form 'unintended'.

Initially, 'intend' meant 'to stretch toward', but over time it evolved into its current meaning of 'to have a plan or purpose'. 'Unintended' thus means 'not having a plan or purpose'.