O-muko (written as '大向う' or '大向こう'; literally, 'the welcome other side') comes originally from seats seen from the stage, and at present, it is used as a term referring to the front seats of the third floor of theatres and to the audience at those seats (in present Kabuki-za Theatre of Tokyo, it refers to the seats for b-class tickets and the seats on the highest balcony for a single act).
大向う（大向こう、おおむこう）とは、芝居小屋の三階正面席、またそこに坐る客を指す隠語・通言（現在の歌舞伎座では、構造上三階Ｂ席から幕見席あたりを指すものとして理解されている。）、つまり大向うとは、舞台上から見た客席の位置に由来する。