'legally-aided' originates from English components: 'legal' (from Latin 'legālis' < 'lēx' meaning 'law') + the adverbial suffix '-ly', and 'aid' (from Old French 'aide' < Latin 'adiūtum' from 'adiuvāre' meaning 'to help') + the participial/adjectival suffix '-ed'.

'legālis' entered Middle English via Old French as 'legal'; 'aide' entered Middle English as 'aid'. The compound adjective 'legally-aided' arose in modern English (20th century) alongside state-funded legal aid schemes, combining 'legally' and 'aided'.

Initially, it literally meant 'aided in a legal sense.' Over time, it became specifically associated with receiving state-funded assistance for legal costs.