I just came across a word new to me, namely yardang, ‘a sharp, irregular ridge of sand or the like, lying in the direction of the prevailing wind in exposed desert regions and formed by erosion by the wind of adjacent less resistant material’ (OED). Naturally, I wanted to know the etymology of this exotic-sounding word, and the OED did not disappoint: “a. Turk., abl. of yar steep bank, precipice.” Now, the Turkish ablative ending is -dan/den (to fall from a cliff is yardan uçmak), so I presume by “Turk.” they mean Turkic, and the -dang ending is from some other Turkic language, a supposition reinforced by the first citation:
1904 S. Hedin Sci. Results Journey in Central Asia I. xxvii. 439 At intervals furrows or trenches in the clay subsoil, called jardangs, traced between long elevations or ridges, crop up amongst the dunes.
So we’re dealing with a Central Asian language. But as far as I can tell, the ablative ending is -dan in Uzbek, Kazakh, Kyrgyz, Uyghur, and Turkmen, and according to this page in The Turkic Languages by Lars Johanson (thank you, Amazon text search!) the Proto-Turkic ablative ending was *-dAn. So is the -ng a mistake by Hedin, picked up by everyone else from him, or is there some dialect that has it?
(I fully realize the recondite nature of this question and the unlikelihood that anyone out there will know the answer, but it never hurts to try, and besides, I wanted an excuse to publicize the word. Isn’t it fun to say? Yardang! Oh, and I got it from this page, via the irreplaceable plep.)