hypocaust

Meanings

1. An underfloor space or flue through which heat from a furnace passes to heat the floor of a room or a bath.
2. An underfloor heating system, even without such an underfloor space or flue, as adapted for modern housing.

Etymology

From Latin hypocaustum, from Ancient Greek ὑπόκαυστον (hupókauston), from Ancient Greek ὑπό (hupó, “underneath”) + καυστόν (kaustón, “burnt offering”).