I did a couple of Google searches, but couldn't find anything about the linguistic origin of this word. I did discover, however, that in Russian this word is written цварнохарно, which would be transliterated, using one of the more common and more user-friendly systems, as tsvarnokharno; in the "scientific" system, this would be cvarnoharno or cvarnoxarno. The z spelling, most likely, is based on German, where the letter z is pronounced /ts/. I doubt the word has Slavic origins; my guess would be that, given Gurdjieff's own nationality, it's Armenian. But sadly, I know nothing of Armenian.