The creature Gothmog at the Siege of Minas Tirith

[Gordis]

Originally Posted by JeffF.

There is also the possibility that the Kingdom of Angmar was named after the inidvidual whose name was Angmar. The name has no previous affiliation with any region in the North and appears only after the Witch King forms it there.
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Edit: Sorry I have overlooked Pitchwife's post and told exactly the same thing: Angmar is certainly a place-name.
Morover, (unlike Morgul) the name Angmar has nothing dark or ominous about it, most likely it refers to the presence of iron in the mountains.

Also note this quote:

‘It was in the beginning of the reign of Malvegil of Arthedain that evil came to Arnor. For at that time the realm of Angmar arose in the North beyond the Ettenmoors. Its lands lay on both sides of the Mountains, and there were gathered many evil men, and Orcs, and other fell creatures. [The lord of that land was known as the Witch-king, but it was not known until later that he was indeed the chief of the Ringwraiths, who came north with the purpose of destroying the Dúnedain in Arnor, seeing hope in their disunion, while Gondor was strong.]’ LOTR, App A

It is clearly said that the lord of Angmar was known as the Witch-King (Aran Morgul in Sindarin I believe), not as "Angmar".