indoor sandals; slippers
Refers to sandals or slippers worn inside the house, typically in traditional Japanese settings. Often used when entering a home or a tatami room.
Please change into indoor sandals at the entrance.
At the ryokan, indoor sandals are provided.
草履 are traditional Japanese sandals worn outdoors, whereas 上草履 are specifically for indoor use.
Compound of 上 (うわ, 'upper' or 'indoor') and 草履 (ぞうり, 'traditional sandals'). The exact historical derivation is uncertain, but the term clearly refers to sandals worn inside the house.