INVINCIBLE DIAMONDS

In classical antiquity, the word adamant had a lot of different meanings. At different points in time, it was used in reference to white sapphire, steel, iron, gold, magnets, various hard stones, and particularly diamonds. In Old English, it meant "very hard stone" in general, and around the 1440s it became an adjective meaning "unmovable" or "inflexible" (this gradually became more figurative). The term comes from Latin adamas, which is also the source of our word diamond, through Old French diamant. Adamas comes from an Ancient Greek word with the same spelling and a definition of "invincible". It's commonly thought that it ultimately comes from the prefix a-, meaning "not", and daman, meaning "conquer" (so "a stone that can not be conquered"), although a Proto-Semitic origin has also been proposed.