'parenthesis' originates from Greek, specifically the word 'parénthesis', where 'para-' meant 'beside' and 'entithenai' meant 'to put in'.

'parenthesis' passed into Late Latin as 'parenthesis', then into Medieval/Modern Latin and Middle English, eventually becoming the English word 'parenthesis' (plural 'parentheses').

Initially it meant 'a putting in beside' (an insertion); over time it came to mean specifically the inserted remark and the pair of marks ( ) used to enclose such insertions.