A fact which is unalterable and a person who is so adamant that he will not change even when persuaded that is an inexorable fact and an inexorable man. It is an adjective. Its first usage dates back to 1545-55.
Meanings of Inexorable
1) Something unalterable
2) Someone unyielding/unmoved/unchanged even by prayers/pleading
Master’s tip to learn Inexorable
Inexorable can be learnt easily by associating it with the character of Lord Voldemort in Harry Potter series. He was one character who did not yield and change even when people pleaded to him for not killing them, he did it anyway.
Also, inexorable can be learnt easily by associating it with the word inflexible, as inexorable person is inflexible.