Ready for your first dose of language autism this year?
The Germanic word for incubus/succubus/sleep paralysis demon is Mahr (German) or marra (Norse) which Anglicized would be merr, mair, or mare. This word is the second half of nightmare and it's of the same Indo-European (or Indo-Aryan) root as the Latin element mort - that being mer- which meant "to rub, wipe" and from there "rub out, wipe away, harm."
The Indo-Europeans (the Over-Ukranians who took over Eurasia on horseback) can also be called the Indo-Aryans or Aryans. This word comes from the reconstructed root arya- (noble, honorable) which in Sanskrit meant "Indian nobility" and from which we get Iran/Iranian. In the 1800s the key early Indo-Europeanist Friedrich Schlegel tied this root to German Ehre (honor) and related Germanic names, supposing the Indo-Europeans may have called themselves the Arra or such. The Nazis took this and ran with it, claiming MUH ERYINZ were North European and using Aryan to mean based. Because of that Aryan and its root were made taboo and stricken from academia. But if Schlegel was right (and there's a fifty-fifty chance he is) than Aryan is with us in everyday words like are, first/fore, rise/raise, early/orient. That's because the root seems to have originally meant "that which is" or "first" leading to the sense "that which comes up first" like "the morning, the east" or warriors who due to their rank or courage are "first among us, first to stand."