接頭辞at-はad-と同じ。 -tornはturnと同じ。依頼人の方を向いて依頼人の利益を代弁する人。
Johnson observed that "he did not care to speak ill of any man behind his back, but he believed the gentleman was an attorney." [Boswell]The double -t- is a mistaken 15c. attempt to restore a non-existent Latin original. Attorney general first recorded 1530s in sense of "legal officer of the state" (late 13c. in Anglo-French), from French, hence the odd plural (subject first, adjective second).