clay bed-warmer with a brazier inside
A traditional Japanese bed-warmer: a cylindrical clay container with holes in the sides, holding a small charcoal brazier. Used to warm bedding before sleep.
In winter, my grandmother would warm the futon with a neko-hibachi.
Compound of 猫 (neko, 'cat') and 火鉢 (hibachi, 'brazier'). The name likely comes from the shape or the way it was kept near the feet like a cat.