From Latin 'internus' (internal) via French — originally a medical student who literally lived inside the hospital, unable to leave.
A student or trainee who works in a professional setting to gain experience.
From French 'interne' (a resident within), from Latin 'internus' (internal, inward). Originally meant a medical student who lived inside the hospital — literally an 'internal' person. The opposite was an 'externe' (a student who went home at night). Key roots
An 'intern' is a prisoner — etymologically speaking. The word means 'one who lives inside' (from Latin 'internus'), and to 'intern' someone means to confine or imprison them. Medical interns literally lived inside the hospital, unable to leave. The word for a concentration camp detainee ('internee') and the word for an unpaid office worker