Well, both "coliero" and "colieri" seem to be common Italian surnames. ("Colieros" could be an English plural of an Italian word, rather like "pizzas"). I can't find a translation of either word into English, but three possibilities present themselves:

1. "Coliero" means "a man from Colio" or some such. Why is he talking about men from Colio? No idea.
2. "Coliero" is the name of a profession or a descriptive attribute, which has become a surname. Find out what the word means, and Doughty makes sense (maybe).
3. "Coliero" was a well-known person and Doughty is using his name as a descriptor: rather as one might talk about a group of British civil servants as "Sir Humphreys". In which case, who was Coliero?

Oh, and a fourth one: it's a typo.

This isn't some form of "collier" (a coal-man), is it? The OED lists this among the usages:

III. attrib. and Comb.: as collier-brig, -ship; collier-built adj.; collier-man, -master, the captain of a coal-ship; collier's faith [med. Lat. fides carbonarii, Ger. köhlerglaube], uninquiring or unreasoning assent to the prevalent religious tenets; blind faith;

1581 HANMER Jesuits Banner Kijb, Not hanging with the *colliers fayth upon the sleeueless coate of the Romish Church. [1603 CHETTLE Eng. Mourn. Garment Diiijb, Onely of the faith that the Colliar profest, which was euer one with the most. [See the story 1621 BURTON Anat. Mel. III. iv. II. vi.] 1680 Observ. ‘Curse Ye Meroz’ 6 [He] proceeds to talk of Faith..but possibly 'tis the Colliers Faith he means all this while.

The Burton reference, which I will let someone else track down, sounds like it could be connected to Doughty.

I found the Italian surname and thought of the "collier" possibility, but neither makes sense in context. He's talking about Greek monks, so the word may be of Greek origin, but I've checked the obvious possibilities in Greek dictionaries and come up empty.

Sure, it could be a typo, but the book is very well proofread (that "monastry" in the same sentence, for instance, is not a typo but an archaic spelling)—and what would it be a typo for?

"koliero" is Esperanto for "clothing" or "fashion", so clearly the word refers to runway models. The "formal" is supporting evidence: models seldom smile.

A surprising number of the results in a Google search for "coliero" are Maltese. It usually seems to be a surname, but it's not all one famous Maltese person. Maybe the surname is concentrated in Malta? Not that that helps at all.

Just to make it clear, Coliero and Colieri are not at all common Italian surnames. In fact, they are practically nowhere to be found in Italy. See http://gens.labo.net/en/cognomi/genera.html?cognome=coliero&t=cognomi

I wonder if colieros was somehow arrived at from καλογεροσ, a Greek word for monk, which also leads to caloyer and caloieros - "The Iland is but small, not aboue five miles in compasse: the chiefe thing it yeeldeth is corn: it hath a port for shipping, and in it is a monastery of Greekish Caloieros"

It says here: http://www.newadvent.org/cathen/10467a.htm , in a rundown of the ranks in a Greek monanstry:
"The kellarios looked after the food."

I wonder if it might be a Frenched-up version of EJP's caloyer / caloieros? It's possible that collier would be the modern word, with colieros being the equivalent of going back and making it sound "more Greek." This is mostly loose speculation on my part, but I don't think it's too implausible.

This is only tangentially related, but I thought it was interesting:

"Soon after midnight, the sound of the semandron echoes in steady rhythm across the wooded valley, a dent in the mountains where scarlet lilies and lush ferns compete in the shade that offers respite from the summer sun. It is still dark of course. Here, as all over the republic, men rise from their beds and make their way to the katholikón. Each utters a steady mantra that picks up the imposing sonority of the semandron. The beat of the wooden hammer on a huge plank of ancient maple calls the devout and the dissolute to morning prayer. In the stricter regime of the more traditional communities, no-one is exempt. Not even the guests who arrived only yesterday from the mainland and are still foot weary from the trail and mind weary from their encounters with Athonite bureaucracy."

that quote was from an article on hiddeneurope.co.uk the comment form didn't like me including the url for some reason.

It's definitely meant for kaloyeros, and I should have thought of that myself. Thanks, EJP!

What interesting timing; the New York Times just had an article on the singing sand dunes.

And Language Log has an interesting posting on some small problems with the said New York Times article.

The OED can't use every obsolete spelling as a headword. Presumably caloyer is the current (1800+) spelling. The older ones differ from it by -i- for -y-, or including the Italian -o/-i, or by haphazard errors. The list of forms is adequately given by the quotations and explained by the etymology.

x: No, you're wrong. 1) Caloyer is not the "current" spelling; have you seen it lately? It may well not have been used since the 19th century; it's certainly thoroughly obsolete. (A Google search reveals a bunch of dictionary entries, taken over from older dictionaries, and a Wikipedia article that "incorporates content from the 1728 Cyclopaedia, a publication in the public domain.") If someone wants to refer to a Greek monk by the native name, they would now presumably a form closer to the Greek kaloyeros, in keeping with the trend towards ever more accurate renditions of local names over the last century. In any event: 2) The entry is specifically for the French loan; both spelling and pronunciation make that clear, and the etymology says it's from French, which in turn is from Italian, which is from Greek. If they want to include forms from Italian and/or Greek, they have to either change the structure of the entry or create a new entry for the latter. As I said.

Perhaps you're not aware that the OED very frequently has separate entries for separate borrowings of the same foreign word, if they're as different in form as caloyer /kaloye/ and kaloyeros /kaloyeros/.

Interesting correspondence between the NYT explanation of the sound ("collisions between sand grains cause the motions of the grains to become synchronized") and Doughty's ("the upper sand sliding down under the foot of the passenger, there arises, of the infinite fretting grains, such a giddy loud swelling sound...").

I'm glad I could be of help. Strangely, it was not more than a few days ago that I first came across the word caloyer, in a novel by Gene Wolfe. If it hadn't been fresh in my mind I probably wouldn't have made the connection with colieros.

Which novel was it? I love Gene Wolfe but haven't read very much.

LH, the word have sipped into Russian through Byzantium Orthodox associations and it means the monk who's responsible for the meals in a monastery.

It was in The Claw of the Conciliator, second volume of The Book of the New Sun - "The executions were to take place at the very center of the festivities, and a dense crowd had already gathered there. A caloyer in red stood beside the scaffold clutching his little formulary; he was an old man, as most of them are."
Mr. Wolfe's books are a treat for anyone with a taste for obscure and archaic words.

Thanks, Tat and EJP respectively!