TTF,
I found this quick little discussion, but it is not definitive:
Chuvash words. Very interesting is, for example, Slovak, Cz. koberec, Pol. kobierzec "carpet". This word reminds the Rus. kover “carpet”, but it is quite visible that the West Slavic words are not borrowed from Russian. Vasmer believes, that the source of the loan word in Russian can be the Old. Chuv. *kavêr - *kabir (Vasmer M., 1964). It would be conceivable for the Slovak and Czech words to be borrowed even earlier from the Bulgarian, but it would be impossible to confidently state this about the Polish word. There is also another explanation. The Old Chuvashian form restored by Vasmer very closely matches the Eng. cover. Hence, the Slovak word can also be from the Old English (i.e. Germanic, which in turn comes from the Türkic) substratum.
~Thadeus