'non-institutional' originates from Modern English, specifically formed from the prefix 'non-' (meaning 'not') + the adjective 'institutional' (from 'institution').

'institutional' is derived from 'institution', which comes from Old French 'institution' and ultimately from Latin 'institutio' (from 'instituere' 'to set up'); the prefix 'non-' is a native English formation borrowed from Latin 'non' meaning 'not', producing the compound 'non-institutional' in modern English.

Initially, 'institution' and its derivatives referred to established arrangements or organizations; over time, the compound 'non-institutional' has come to specifically denote being outside or independent of such formal institutions.