firebox

/F AY1 ER0 B AA0 K S/
noun
  1. 1

    The chamber of a steam engine, or a steam locomotive, in which the fuel is burned.

  2. 2

    The part of a fireplace where the fuel is burned.

  3. 3

    A redheaded woman (by synecdoche, pars pro toto), or her red pubic hair.

Source: https://en.wiktionary.org/wiki/firebox