Coal
Old English col (in the senses ‘glowing ember’ and ‘charred remnant’), of Germanic origin; related to Dutch kool and German Kohle . The sense ‘combustible mineral used as fuel’ dates from Middle English.
wiktionary
From Middle English cole, from Old English col, from Proto-West Germanic *kol, from Proto-Germanic *kulą (compare West Frisian koal, Dutch kool, German Kohle, Danish kul), from *ǵwelH-(“to burn, shine”).
Compare Old Irish gúal(“coal”), Lithuanian žvìlti(“to twinkle, glow”), Persian زغال (zoğâl, “live coal”), Sanskrit ज्वल्(jval, “to burn, glow”), Tocharian B śoliye(“hearth”), all from the same root.
etymonline
coal (n.)
Old English col "charcoal; live coal, piece of wood or other combustible substance, either burning or having been burned," from Proto-Germanic *kula(n) (source also of Old Frisian kole, Middle Dutch cole, Dutch kool, Old High German chol, German Kohle, Old Norse kol), from PIE root *g(e)u-lo- "live coal" (source also of Irish gual "coal").
Meaning "solid mineral consisting of fossilized carbon, combustible and used as fuel," is from mid-13c. The thing itself is mentioned 370 B.C.E. by Theophrastus in his treatise "On Stones" under the name lithos anthrakos (see anthrax). Traditionally good luck, coal was given as a New Year's gift in England, said to guarantee a warm hearth for the coming year.
The phrase drag (or rake) over the coals was a reference to the treatment meted out to heretics by Christians. To carry coals "do dirty work," also "submit to insult" is from 1520s.
To carry coals to Newcastle "add to that of which there is already an abundance, do unnecessary labor " (c. 1600) is a local variant on an ancient class of expression: Latin had in litus harenas fundere "pour sand on the beach," in silvam ligna ferre "carry wood to the woods;" Greek glauk eis Athenas "owls to Athens." Newcastle is in the midst of a great coal-producing region. The ancient view is not necessarily the modern one. A historian, noting that the medieval English exported manufactured cloth to the Low Countries, where weaving was a major industry, writes, "it is always sensible to send coals to Newcastle or owls to Athens if you can be sure of underselling the locals" [George D. Painter, "William Caxton," 1976]
