'legitimately-acquired' originates from the combination of 'legitimate' and 'acquire', where 'legitimate' comes from Latin 'legitimus', meaning 'lawful', and 'acquire' from Latin 'acquirere', meaning 'to gain'.

'legitimus' transformed into the Old French word 'legitime', and eventually became the modern English word 'legitimate'. Similarly, 'acquirere' transformed into the Old French 'acquerre', and eventually became the modern English word 'acquire'.

Initially, 'legitimate' meant 'lawful' and 'acquire' meant 'to gain', and these meanings have largely remained the same in modern usage.