In John Buchan's Greenmantle, Hannay, a British officer, is on a secret mission in Turkey during the First World War. Britain sent him there because it suspects that Germany is planning a religious war with the help of a Muslim prophet named Greenmantle, who has four ministers and the aid of a German woman called Hilda von Einem. Sandy, Hannay's friend, was a leader of the Islamic orthodox coterie and is now talking about that prophet:
“I never saw such a man. He is the greatest gentleman you can picture, with a dignity like a high mountain. He is a dreamer and a poet, too—a genius if I can judge these things. I think I can assess him rightly, for I know something of the soul of the East, but it would be too long a story to tell now. The West knows nothing of the true Oriental. It pictures him as lapped in colour and idleness and luxury and gorgeous dreams. But it is all wrong. The Kaf he yearns for is an austere thing. It is the austerity of the East that is its beauty and its terror ... It always wants the same things at the back of its head. The Turk and the Arab came out of big spaces, and they have the desire of them in their bones. They settle down and stagnate, and by the by they degenerate into that appalling subtlety which is their ruling passion gone crooked. And then comes a new revelation and a great simplifying. They want to live face to face with God without a screen of ritual and images and priestcraft. They want to prune life of its foolish fringes and get back to the noble bareness of the desert. Remember, it is always the empty desert and the empty sky that cast their spell over them—these, and the hot, strong, antiseptic sunlight which burns up all rot and decay. It isn’t inhuman. It’s the humanity of one part of the human race. It isn’t ours, it isn’t as good as ours, but it’s jolly good all the same. There are times when it grips me so hard that I’m inclined to forswear the gods of my fathers!
I think it's some Ottoman word, but I can't find a suitable meaning for it in this context!