There is a theory that the name Makunouchi-bento comes from the fact that people who saw Noh and Kabuki (traditional drama performed by male actors) enjoyed this special bento during intervals (between acts), that is, Makuai, and this theory is widely accepted..
能や歌舞伎を観覧する人々が幕間（まくあい）にこの特製の弁当を食べていたため「幕の内弁当」と呼ばれるようになったという説が有力である。