'illicitly-gained' originates from the Latin word 'illicitus,' meaning 'not allowed,' combined with 'gain,' from Old French 'gaigner,' meaning 'to earn or win.'

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

Initially, 'illicit' meant 'not allowed by law,' and 'gain' meant 'to earn or win.' Together, they describe something obtained through illegal means.