Proto-Indo-European root meaning "to heat, warm."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit gharmah "heat;" Old Persian Garmapada-, name of the fourth month, corresponding to June/July, from garma- "heat;" Hittite war- "to burn;" Armenian jerm "warm;" Greek thermos "warm;" Latin formus "warm," fornax "oven;" Old Irish fogeir "heated;" Old English bærnan "to kindle."
goddess of ovens in ancient Rome, from Latin fornax "furnace, oven, kiln" (from PIE root *gwher- "to heat, warm"). The dim constellation (representing a chemical furnace) was created by French astronomer Nicolas Louis de La Caille in 1752.
late 13c., "furnace;" late 14c., "smoke vent of a fireplace, vertical structure raised above a house for smoke to escape to the open air;" from Old French cheminee "fireplace; room with a fireplace; hearth; chimney stack" (12c., Modern French cheminée), from Medieval Latin caminata "a fireplace," from Late Latin (camera) caminata "fireplace; room with a fireplace," from Latin caminatus, adjective of caminus "furnace, forge; hearth, oven; flue," from Greek kaminos "furnace, oven, brick kiln," which is of uncertain origin.
From the persistence of the medial i in OF. it is seen that the word was not an ancient popular word, but a very early adoption of caminata with subsequent phonetic evolution [OED]
Jamieson  notes that in vulgar use in Scotland it typically was pronounced "chimley." From the same source are Old High German cheminata, German Kamin, Russian kaminu, Polish komin. Chimney-corner "space beside a fireplace" is from 1570s.