"Diamond" comes from the Greek adamao, which signifies "I tame" or "I subdue". From ancient times, the adjective adamas was used to describe the hardest substance known to men. It eventually became a synonym for the word diamond. It is believed that Adamas previously referred to the second hardest mineral, corundum (the gem variety is sapphire) or to something else altogether. Due to this problem of uncertainty surrounding the names, it is difficult to trace the history of the diamond.