Yours, Etc.: Origins and Uses of 8 Sign-Offs
Old English col "charcoal, live coal," from Proto-Germanic *kula(n) (cf. 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" (cf. Irish gual "coal").
Meaning "mineral consisting of fossilized carbon" is from mid-13c. First 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 (c.1600) Anglicizes Greek glauk eis Athenas "owls to Athens."
A dark-brown to black solid substance formed from the compaction and hardening of fossilized plant parts in the presence of water and in the absence of air. Carbonaceous material accounts for more than 50 percent of coal's weight and more than 70 percent of its volume. Coal is widely used as a fuel, and its combustion products are used as raw material for a variety of products including cement, asphalt, wallboard and plastics. See more at anthracite, bituminous coal, lignite.
It is by no means certain that the Hebrews were acquainted with mineral coal, although it is found in Syria. Their common fuel was dried dung of animals and wood charcoal. Two different words are found in Hebrew to denote coal, both occurring in Prov. 26:21, "As coal [Heb. peham; i.e., "black coal"] is to burning coal [Heb. gehalim]." The latter of these words is used in Job 41:21; Prov. 6:28; Isa. 44:19. The words "live coal" in Isa. 6:6 are more correctly "glowing stone." In Lam. 4:8 the expression "blacker than a coal" is literally rendered in the margin of the Revised Version "darker than blackness." "Coals of fire" (2 Sam. 22:9, 13; Ps. 18:8, 12, 13, etc.) is an expression used metaphorically for lightnings proceeding from God. A false tongue is compared to "coals of juniper" (Ps. 120:4; James 3:6). "Heaping coals of fire on the head" symbolizes overcoming evil with good. The words of Paul (Rom. 12:20) are equivalent to saying, "By charity and kindness thou shalt soften down his enmity as surely as heaping coals on the fire fuses the metal in the crucible."