'non-negotiable' originates from the prefix 'non-' meaning 'not' and the word 'negotiable' which comes from Latin 'negotiabilis', meaning 'able to be transacted'.

'negotiabilis' transformed into the French word 'négociable', and eventually became the modern English word 'negotiable'. The prefix 'non-' was added to form 'non-negotiable'.

Initially, 'negotiable' meant 'able to be transacted or discussed', but with the prefix 'non-', it evolved to mean 'not open to discussion'.