hot-water bottle
A container filled with hot water and used to warm a bed or body; traditionally made of metal or ceramic, now often plastic.
On cold nights, I put a hot-water bottle in my futon and go to sleep.
My grandmother uses an old-fashioned metal hot-water bottle.
Standard modern spelling; the kanji 湯 (hot water) is combined with hiragana たんぽ.
Rarely used kanji form; the characters 湯婆 literally mean 'hot-water old woman', reflecting the traditional shape.
Derived from Chinese 湯婆子, the name of a hot-water warming vessel, through adaptation and shortening in Japanese. The spellings 湯婆 and 湯湯婆 reflect this Chinese source.