From Greek 'adamas' (unconquerable) — 'a-' (not) + 'daman' (to tame). Originally the hardest substance imaginable.
Refusing to be persuaded or to change one's mind; utterly unyielding.
From Latin adamantem (accusative of adamas), from Greek adamas (unconquerable, the hardest substance), from a- (not) + daman (to tame, conquer), from PIE *demh₂- (to tame, to domesticate). In Greek poetry adamas denoted an impossibly hard mythic substance — sometimes iron, sometimes the metal of the gods. Medieval writers identified it with the diamond, but Diamond itself entered English via a separate branch: Old French diamant ← Vulgar Latin *diamas ← *adimas ← Greek adimas, a colloquial contraction