Word Origin & History
parenthesis1550, "words, clauses, etc. inserted into a sentence," from M.Fr. parenthèse, from L.L. parenthesis "addition of a letter to a syllable in a word," from Gk. parenthesis, lit. "a putting in beside," from parentithenai "put in beside," from para- "beside" + en- "in" + tithenai "put, place," from
PIE base *dhe- "to put, to do" (see
factitious). Extension of the word to the curved brackets that indicate the words inserted is from 1715.