Who in Middle-earth knows the Istari's origin?

Question

In the Middle-earth universe, there are a handful of wizards who work in various ways to fight evil. Out of universe, we know these wizards to be Istari, Maia who are in Middle-earth working to defeat Sauron, and we know this thanks to The Silmarillion which explains the origins of Middle-earth.

In universe though, I'd expect this sort of knowledge to be pretty rare. Do we know how rare it is? Who in Middle-earth knows that these wizards are Istari, and the ramifications of this? I'm not looking for a list of specific individuals here, I seek more a list of groups of people.

For example, I'd expect the Noldor who remain in Middle-earth to know what's up with the Istari, since it's part of their personal past. But do any dwarves know? Do any humans? What about Rohan's royalty? The Stewards of Gondor?

Answer 1

The only people (and yes, it's individuals, not groups) who are recorded as having known were Círdan, Elrond and Galadriel; from Rings of Power:

Even as the first shadows were felt in Mirkwood there appeared in the west of Middle-earth the Istari, whom Men called the Wizards. None knew at that time whence they were, save Círdan of the Havens, and only to Elrond and to Galadriel did he reveal that they came over the Sea.

The Istari essay in Unfinished Tales establishes that it was quite some time before Círdan even told the other two:

For they came from over the Sea out of the Uttermost West; though this was for long known only to Círdan, Guardian of the Third Ring, master of the Grey Havens, who saw their landings upon the western shores.

The name "Olórin" was, however, well-known in Gondor, per Faramir's statement in the Two Towers:

'Mithrandir we called him in elf-fashion,' said Faramir, 'and he was content. Many are my names in many countries, he said. Mithrandir among the Elves; Tharkun to the Dwarves; Olórin I was in my youth in the West that is forgotten, in the South Incanus; in the North Gandalf; to the East I go not.'

Although Tolkien notes that '"The West" here plainly means the Far West beyond the Sea, not part of Middle-earth; the name Olórin is of High-Elven form', it is not established whether or not those in Gondor had made the inevitable connection.

Answer 2

Like Jimmy Shelter said, Cirdan, Elrond and Galadriel knew.

Since Sauron himself is a Maia, he would know about the Istari's origin as well. Apart from them, the books do not make clear if anybody else knows. However, a few others, if not knowing who or what Gandalf was exactly at least probably knew that he was not man or elf:

• Glorfindel. Not only did he slay a Balrog (who, according to some theories, might have been a fallen Maia) in the first age and then return to Middle-Earth again via the Undying lands; no, Gandalf had this to say about him when at the Council of Elrond:

In Rivendell there live still some of his chief foes: the Elven-wise, lords of the Eldar from beyond the furthest seas. They do not fear the Ringwraiths, for those who have dwelt in the Blessed Realm live at once in both worlds, and against both the Seen and the Unseen they have great power.

So he likely knew too.

• Aragorn. He knows the lore very well and since Luthien - one of his ancestors - was a Sindarin elf whose mother was Melian the Maia an Aragorn knows the story of Beren and Luthien well and furthermore has for a long time been a close friend of Gandalf, he most likely knows about the Istari's origins.

• Tom Bombandil. 'Nough said.

• Treebeard. He calls the White Wizard "Young Master Gandalf" in TTT and was the oldest living thing in Middle-Earth (apart from Bombandil). He is probably the most unlikely from this list to know about the origins of the Istari since the Ents never had any dealing with the Valar or Maia. It might as well be that Treebeard never cared about who Gandalf really was and where he came from.

• The Hobbits - at least Merry and Pippin - certainly did not know. At one moment (in TTT or RotR) Pippin (or Merry? difficult to hold those 2 apart) asked himself how old Gandalf actually was and where he came from. However, he never gets to ask.

Answer 3

To further confirm what @DarthSatan said, another source from Unfinished Tales (Part II, "The Istari") explicitly says:

"...they belonged solely to the Third Age and then departed, and none save maybe Elrond, Círdan and Galadriel discovered of what kind they were or whence they came"

Answer 4

Frodo knew a bit. At Bag End he said that Saruman had fallen into evil but was of a nature or type of being that Hobbits should revere and not attack:

"No, Sam!" said Frodo. "Do not kill him even now. For he has not hurt me. And in any case I do not wish him to be slain even in this evil mood. He was great once, of a noble kind that we should not dare to raise our hands against. He is fallen, and his cure is beyond us; but I would still spare him, in the hope that he may find it."

So he obviously had learned something about the nature of the Istari.

Added Aug. 14, 2019:

See also Here: https://english.stackexchange.com/questions/295737/ol%C3%B3rin-i-was-in-my-youth-in-the-west-that-is-forgotten-what-is-forgotten1

and Here: When did Bilbo and Frodo learn that Gandalf was a Maia?2

Answer 5

A small addition that all the other answers have ignored (or did not think to include):

Since we’re simply listing who in Middle Earth knew of the origins of the Istari, with no further narrowing down, another group is of course the Istari themselves.

They are in Middle Earth, and they quite naturally know of their own history and origins, even if it does seem at times (especially right after Gandalf’s rebirth) that it seems very far off and unreal to them.