A chimney is the long, vertical, tunnel-like opening above a fireplace that provides a safe pathway for smoke — and the occasional Santa. It is also the name of the curvy glass flue in a hurricane lamp.
Ever since the use of fire indoors, it has been important to build a chimney to allow the smoke to escape. The word chimney comes ultimately from the Greek kaminos, "furnace," and in 13th-century Old French it became the more familiar looking cheminee, "fire place." As chimney fires became a serious problem, the chimney sweep became an important person, cleaning the soot from chimneys. Oh, and dancing on the rooftops. (Or not.)