Specifically refers to the seats closest to the sumo ring, where spectators sit on cushions on the floor and may get sand kicked onto them.
Watching from a ringside seat, you can feel the power of the wrestlers up close.
Compound of 砂 (sand), かぶり (from 被る, to cover or be covered with), and 席 (seat). The name comes from the fact that spectators in these seats may be showered with sand kicked up by the wrestlers.