noun
married couple; husband and wife
Archaic term for a married couple, often used in classical poetry and literature. Not used in modern everyday speech.
妹背の契りを交わす。
They exchange vows as husband and wife.
noun
brother and sister; siblings
Archaic term for a brother and sister pair, especially in classical contexts. The word emphasizes the close bond between siblings.
妹背の仲睦まじい様子が描かれている。
The close relationship between the brother and sister is depicted.
The term いもせ is composed of 妹 (いも, younger sister) and 背 (せ, originally meaning 'back' but used in old Japanese to refer to a husband or brother). The exact historical derivation is uncertain, but it appears in classical literature to denote a close pair, either a married couple or siblings.