multiple layers of fences; fences within fences
Literary and historical term referring to a defensive or symbolic arrangement of layered fences, often appearing in classical poetry and mythology. Not used in everyday modern Japanese.
In the Kojiki, there is a scene where multiple layers of fences are built.
In waka poetry, 'yaegaki' is sometimes used with the image of fences layered many times over.
Compound of 八重 (yae, 'many layers') and 垣 (kaki, 'fence'). The exact historical origin is uncertain, but the term appears in classical Japanese literature and mythology.