Chainmail to distinguish it from scale mail, ring mail or splint and scale? I know Italian armorers had separate terms.
Some of those archetypes – particularly monsters – come down from the bronze age (some probably predate writing). A Tolkien (or whoever) can rigidise the description, and set a species in stone, but certain characteristics have migrated in folk legend across continents, suggesting Jungian necessities. The stupidity of trolls and ogres is an essential part of their origins – I don't know why, a bright troll organising drug heists from under a suspension bridge, or a wise old ogre teaching junior school would seem perfectly acceptable models to me, but mythology evolves to suit its environment, and the traditional models.
Sometimes because of genuine encounters; the lack of iodine in the salt in alpine Switzerland and south Germany led to thyroid deficiencies: cretinism, dwarfism, giants; the Neibelung have a (tenuous) basis in reality (but they wouldn't have been on the Rhine, where sea salt was widespread). Others, such as dragons, seem to fill a need in society. It is almost safer to invent an entirely new species, precisely tailored to the requirements of your story, than suggest that elves are not universally silvatic excellent archers, or that dwarves don't spend the majority of their time underground.
My wizard type is kind of incomprehensible because he insists on using archaic words (He is eight-hundred years old and flips between slang, big words and old words from their country's past) He will translate when asked though.
