Finrod? Inglor? Gnomes? Noldor?

I was reading the fragment of the Lay Of Leithian that I have. At first King Felagund's name was given as Inglor, and Finrod was his father. But at a later stage, the poem says:

"The captives sad in Angband mourn.
Thunder rumbles, the fires burn ---
And Finrod fell before the throne."

Now it's Finrod Felagund.

Similarly, the Elves start off being called Gnomes, and are later called Noldor.

Tolkien changed stuff around, a LOT. As another instance: Strider was once to be a hobbit named Trotter...