'mutually-decided' originates from the combination of 'mutual' and 'decide', where 'mutual' comes from Latin 'mutuus' meaning 'borrowed, lent' and 'decide' from Latin 'decidere' meaning 'to cut off'.

'mutuus' transformed into the Old French word 'mutuel', and eventually became the modern English word 'mutual'. 'Decidere' transformed into the Old French word 'decider', and eventually became the modern English word 'decide'.

Initially, 'mutual' meant 'borrowed or lent', but over time it evolved into its current meaning of 'shared by two or more parties'. 'Decide' has largely retained its original meaning of 'to make a choice or judgment'.