345: Diomond and adamant Nov 18, 2016

Diamonds are the hardest substance known; some diamonds are even cut by other diamonds. Etymologically speaking, the word 'diamond' is related to the word 'adamant'. 'Adamant' comes from Old English ultimately from the Greek word 'adamas, adamant' which means ‘untamable, invincible’. This word was later used to denote the hardest metal or stone. Marvel comics used this information for the fictional metal, 'adamantium', which in the superhero-universe is the hardest metal.
The phrase "to be adamant" was only used starting in the 1930's but the adjective was used colloquially since the 16th century.