The story
Japanese 幕内 (maku-uchi まくうち, "inside the curtain"), from Middle Chinese 幕 (mak "curtain", "covering") + Japanese うち (uchi "inside").
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: The highest division of sumo wrestling, above juryo, comprising the yokozuna, ozeki, sekiwake, komusubi and maegashira ranks. Full definition →
Japanese 幕内 (maku-uchi まくうち, "inside the curtain"), from Middle Chinese 幕 (mak "curtain", "covering") + Japanese うち (uchi "inside").
Etymology from Wiktionary, CC BY-SA 4.0.