'encasement' originates from English, specifically from the verb 'encase' + the noun-forming suffix '-ment', where 'en-' meant 'in, into' and 'case' came via Old French/Late Latin from 'capsa' meaning 'box'.

'encase' developed in English (mid 17th century) from en- + 'case' (from Old French/Late Latin 'capsa' 'box'), and the suffix '-ment' (from Old French/Latin '-mentum') was later added to form the noun 'encasement' meaning 'the act or result of enclosing'.

Initially it referred specifically to placing something in a case or box; over time it broadened to mean any kind of enclosing covering or protective casing.