'intentionally-assisted' is a compound formed from 'intentionally' + 'assisted'. 'Intentionally' descends from 'intentional', from Latin 'intentio' (from 'intendere' meaning 'to stretch toward, aim at'), and 'assisted' comes from Old French 'assister' (from Latin 'adsistere'/'assistere' meaning 'to stand by, help').

'intentio' (Latin) > 'intention' (Middle English via Old French/Latin) > 'intentional' > 'intentionally'; and Latin 'adsistere' > Old French 'assister' > English 'assist' > past participle 'assisted'. These elements were later combined in English as the compound adjective 'intentionally-assisted'.

Initially, the roots meant 'to aim or direct attention' (intent-) and 'to stand by or help' (assist-); over time the compound came to mean 'helped deliberately' rather than any accidental or incidental assistance.