'illicitly-backed' originates from the word 'illicit,' which comes from Latin 'illicitus,' meaning 'not allowed.' The suffix '-ly' is used to form adverbs, and 'backed' is derived from the verb 'back,' meaning 'to support.'

'illicitus' transformed into the Old French word 'illicite,' and eventually became the modern English word 'illicit.'

Initially, 'illicit' meant 'not allowed by law,' and this meaning has largely remained the same in modern usage.