The Elvish prefix Mor means Black but there are many places it is used. Here are some of them.

In The Lord of the Rings this meant Black Pit; another time it meant Black Gulf.

This name can be seen in e.g. Minas Morgul which was what was once Minas Ithil but after being captured by the Nazgûl it was the Tower of (Black) Sorcery (though it had other names).

Sam encounters this just as he enters Mordor. On pg. 899 of the 50th anniversary edition of The Lord of the Rings (HarperCollins Publisher) it's described like this:

Hard and cruel and bitter was the land that met his gaze. Before his feet the highest ridge of the Ephel Dúath fell steeply in great cliffs down into a dark trough, on the further side of which there rose another ridge, much lower, its edge notched and jagged with crags like fangs that stood out black against the red light behind them: it was the grim Morgai, the inner ring of the fences of the land. Far beyond it, but almost straight ahead, across a wide lake of darkness dotted with tiny fires, there was a great burning glow; and from it rose in huge columns a swirling smoke, dusty red at the roots, black above where it merged into the billowing canopy that roofed in all the accursed land.

Sam was looking at Orodruin, the Mountain of Fire. [...]

Earlier known as Melkor ('He Who Arises In Might'), at that point mightiest of the Valar, Fëanor named him Morgoth after he colluded with Ungoliant(e) to darken the world and then steal the Silmarils (and other jewels but it was the Silmarils that were most coveted): Black Enemy, Black Foe; and no longer was he considered part of the Valar.

This was the Black Gate of Mordor (Black Land, see next section): this was where Frodo with Gollum and his servant Sam first went but because it was closed Gollum would lead them to the other way; they would be captured by Faramir Captain of Gondor and they would be released and then Gollum would lead them on towards Mordor.

Dor means Land, Country. Here are some examples.

This was if I am remembering right Stone Land. Its earliest name was Ond (and then it was Ondor before becoming Gondor). This was a kingdom in the South that is also where Aragorn was crowned King of the reunited kingdoms and where he wed the Lady Arwen of Rivendell.

As above prefix Mor suggests this means Black Land. This would be where the Mountain of Fire was, which is where the One Ring was forged in secrecy (to rule over the other Rings of Power that had been made by the Elves with Sauron's guidance).

This word which means Tree-folk derives from the Old English word eoten which means giant. The history of this is more complicated and I have a section in my commentary on the history of The Lord of the Rings document.

Fangorn is elvish literally for beard-(of)-tree.

This is one of the many amazingly brilliant names by Tolkien and it's my favourite too! It goes beyond what most people probably even realise. This is how he is introduced and his explanation in The Lord of the Rings:

'Ha, hmm, my friends, let us go for a walk!' he said. 'I am Bregalad, that is Quickbeam in your language. But it is only a nickname, of course. They have called me that ever since I said yes to an elder Ent before he had finished his question.

But that's not the best part! To understand this you have to take a look at the dictionary:

quickbeam noun
another term for mountain ash (sense 1).

mountain ash noun
1 a small deciduous tree of the rose family, with compound leaves, white flowers, and red berries. Compare with rowan.

rowan (also rowan tree) noun
a small deciduous tree of the rose family, with compound leaves, white flowers, and red berries. Compare with mountain ash.

The keyword is 'rowan': there were rowan-trees in Quickbeam's home! Is this actually surprising that Tolkien knew this? No I don't think so. Not only was he a philologist and lexicographer but he also loved trees!

Here I include some Hobbit related names and terms and what they mean.

Deriving from the OE adjective samwís 'stupid, dull, foolish' it means 'halfwise, simple'.

OE adjective hámfæst 'resident, settled in or owning a house' and it means 'stay-at-home'.

In The Lord of the Rings in the chapter The Scouring of the Shire we come across the term Shirriff: hobbit police. This derives from Shire + 'reeve':

reeve noun
mainly historical a local official, in particular the chief magistrate of a town or district in Anglo-Saxon England

Lob is an old word for 'spider' so it literally means She spider