STRONGS NT 440: ἄνθραξ

ἄνθραξ, ἄνθρακος, ὁ, coal (also, from Thucydides and Aristophanes down, ἄνθραξ πυρός a coal of fire i. e. a burning or a live coal), live coal; Romans 12:20 ἄνθρακας πυρός σωρεύειν ἐπί τήν κεφαλήν τίνος, a proverbial expression, from Proverbs 25:22, signifying to call up, by the favors you confer on your enemy, the memory in him of the wrong he has done you (which shall pain him as if live coals were heaped on his head), that he may the more readily repent. The Arabians call things that cause very acute mental pain burning coals of the heart and fire in the liver; cf. Gesenius in Rosenmüller's Biblical-exeg. Repert. i., p. 140f (or in his Thesaurus i. 280; cf. also BB. DD. under the word ).