Unfortuneately my mind is such as to rarely provide documentary or referential sources; a constant difficulty for those who recieve communication from me....
There is recurrent confusion around the term Tartar; for many centuries it is commonly used to refer to the primarily Turkic peoples of the Eurasian stepper, commonly including, but not limitted to Kazaks, Turks, Huigars, Mongols, etc. Also for centuries, it has been used to refer to specific tribes, often somewhat localized of course.
There seem to be 3 possible explanations that come to mind:
1/Some Tartars live nearby. You are not a Tartar. They are Tartars, and that's enough for you; your people don't know their tribal name; you don't know any other Tartars; you think they're "Tartars."
2/There are tribes that seem to have no other name but "Crimean Tartars" or "Blue Tartars" (though how much this is a foriegn inaccuracy is unclear). Such tribes may become in shorthand "Tartars" to someone who is unaware of the broader implications of the term. Essentially similar to #1
3/It was originally the name of one tribe, and got more generally applied, as with Roman, Zulu, Mongol....the problem I see with this is this usually occurs through conspicuous conquest, and we know other names for conspicuously conquering/ruling Tartar tribes, like Mongol and Turk?.....
All this confusion is not helped by the fact that these people, their culture, and their vast historical influence, are largely ignored in the "West", and after the irritating way of "Science" which seeks boundaries more often than centers (by it's defining nature), who get attached to the other cultural areas they border, rather than being seen as their own; so Huigars and Manchus are viewed as Chinese, Cossaks and Magyars as Slavs/Europeans, Turks as psuedo-Arabic, etc. Of course there's blending along cultural borders, but this case seems to be only looked at in that one way; as a vast frontier between cultural realms, rather than a valid and important realm in its own right, and I think that this is, well, bogus.
So Tartar Tartar Tartar, say I; let's all eat a bagel and some yogurt
