'reclusory' originates from Medieval Latin, specifically the word 'reclusorium', where the prefix/root 're-' meant 'back' or 'again' and 'cludere' (from Latin 'recludere') meant 'to shut'.

'reclusory' changed from the Medieval Latin word 'reclusorium' into Middle English as 'reclusorie'/'reclusory' and eventually became the modern English 'reclusory'. The earlier root is Latin 'recludere' > past participle 'reclusus' which produced Old French and Medieval Latin forms.

Initially it referred specifically to a place 'shut apart' for a religious recluse; over time the word retained this core meaning of a secluded dwelling but has become rare and somewhat archaic in modern usage.