Ghân-buri-Ghân is the headman of the Woses, the Wild Men of the Woods who live in Druadan Forest in East Anórien, in Gondor. He is "gnarled as an old stone, and the hairs of his scanty beard straggled on his lumpy chin like dry moss" (5.5.11). He can speak Common Speech, but his voice is guttural and choppy. He wears only a grass skirt around his waist.
The reason Ghân-buri-Ghân wants to join with Théoden is because his people absolutely hate the orcs. It's an enemy-of-my-enemy-is-my-friend situation. He tells Théoden: "Kill gorgûn in woods, hate orc-folk. You hate gorgûn too. We help as we can" (5.5.13). In exchange for this assistance, Théoden promises him rewards if Minas Tirith stands at the end of the war.
Ghân-buri-Ghân asks for only one reward for his help: that Théoden and his people leave the Woses alone. He just wants Théoden's people to stop hunting the Wild Men as though they are animals. (We can't believe Ghân-buri-Ghân has to negotiate with the Riders of Rohan to stop his people from being hunted. How much more obviously wrong can you get?)
Merry observes that Ghân-buri-Ghân looks a lot like the Púkel-men of Dunharrow, the long-forgotten statues that line the steep road up to Dunharrow. He wonders if Ghân-buri-Ghân is "a creature descended in true line through endless years from the models used by the forgotten craftsmen long ago" (5.5.11).
In other words, Merry wonders if Ghân-buri-Ghân's ancestors were the models for the carvers of the Púkel-men. It never occurs to him that Ghân-buri-Ghân's people might have the skill to make those statues for themselves. In fact, Merry even thinks of Ghân-buri-Ghân as a "creature" rather than a person. And this assumption, that the Wild Men are closer to animals than to people, continues throughout the novel's portrayal of Ghân-buri-Ghân and the Woses.
Ghân-buri-Ghân's people are skilled trackers. Still, the narrator emphasizes that even that talent is more animal-like than human. Only "Wild Men and beasts" now know the paths that Ghân-buri-Ghân wants to show the Riders of Rohan. And at one point, Ghân-buri-Ghân stands looking up "like some started woodland animal snuffling a strange air" (5.5.41)—again, as though he is an animal rather than a man.
The text's description of Ghân-buri-Ghân's lumpy face and squat body also makes him sound almost half-human. The only other characters we have met so far with short legs and fat arms are the orcs of Mordor (see Grishnákh, "a short, crook-legged creature, very broad with long arms that hung almost to the ground," The Two Towers 3.3.27). What is more, Ghân-buri-Ghân can't even laugh like a human. Merry hears him making "a curious gurgling noise, and it seemed that he was laughing" (5.5.35).
This depiction of the Wild Men as semi-animal troubles us, if we're being honest. It's like something from a stereotypical early movie or book that depicts native peoples as savages, needing to be civilized.
Still, we will say that, even if Tolkien uses some condescending and ugly language to describe the Woses, Ghân-buri-Ghân is an interesting and even ambiguous character. He doesn't have a lot of the things that Tolkien's noble characters usually have. He is neither tall, nor fair, nor well educated in elvish or Númenorean lore.
But at the same time, Ghân-buri-Ghân does have a strong sense of honor and fair play, and he doesn't let the Riders of Rohan push him around, no siree. When Éomer expresses surprise that the Woses can understand the size of the force threatening Gondor, Ghân-buri-Ghân replies firmly: "Wild men are wild, free, but not children" (5.5.17). Basically, Ghân-buri-Ghân tells Éomer to stop making stupid assumptions. And his basic desire for his people to be left alone after the war is moving, both for Théoden and for us, the readers.
So while Ghân-buri-Ghân fits into many unfair stereotypes, with his lack of clothes and his broken speech, he is also keen and filled with genuine loathing for orcs and injustice. He is a good man, even if his portrayal is a bit biased and politically incorrect.
Aragorn recognizes Ghân-buri-Ghân's goodness at the end of The Return of the King. As Aragorn travels to Rohan with a huge chunk of his household, he stops near Amon Dîn and announces that, henceforward, the Forest of Drúadan will belong to Ghân-buri-Ghân and his people alone. They now have the right to keep the forest to themselves; everyone else has to keep out unless they are invited in by the Wild Men. So at least the Woses can keep on living free, as they choose.