The word was first recorded in English by 900, from Latin. It appears in King Alfred’s translation of Gregory’s Pastoral Care, in a line saying that a hard stone cannot be cut by any iron.
Old French had a form of the word by the twelfth century, meaning both a diamond and a magnet. English borrowed it again by the middle of the fourteenth century, and in about 1385 Chaucer’s Knight’s Tale described an everlasting door made of it.
In Greek, the source word was an adjective meaning ‘unbreakable’. Its origin is uncertain, though one theory builds it from a prefix meaning ‘not’ and a verb meaning ‘to conquer’, which traces to a Proto-Indo-European root, *deme-, ‘to break horses’.
TAME and DAUNT come from that same root. TAME goes back to an Old English word for ‘domesticated’, and by about 1200 it described people held in subjection. DAUNT entered English about 1300, from Old French, meaning to vanquish, and goes back to a Latin verb meaning ‘to tame’.
