火燵掛布[kotatsugake] cover for kotatsu
火燵布団[kotatsubuton] cover for kotatsu
火燵[kotatsu] kotatsu

掘炬燵[horigotatsu] low, covered table placed over a hole in the floor of a Japanese-style room
置火燵[okigotatsu] portable brazier
炬燵虫[kotatsumushi] someone who curls up under a kotatsu all winter