Ossetians are the only linguistically Iranic people of the north caucasus; Chechen and Abkhaz languages fall under the caucasian category. Meanwhile there are also Turkic-speakers like Karachays, Balkars and Kumyks.
Here's a convenient linguistic map for reference:
The thing to keep in mind though is that despite the linguistic diversity the northern caucasians are all very culturally similar: you'll find they have really, really similar traditional dress, food, customs, dances, etc, etc. Plus they're very similar in appearance and behaviour/temperament. So even though Ossetians may speak an Iranic language and the Karachays a Turkic one, it's likely that both groups descend from aboriginal highlanders rather than from Iranic or Turkic steppe cultures.
For instance, with the Karachays and Balkars, they're linguistic 'outsiders' in that they don't speak a Caucasian language, yet they live in the highest parts of the mountains, while 'native' Caucasian speakers, like Chechens, Cherkessians, Ingushetians and Kabardins live quite a way further down. I.E. the language is not a reliable indicator of ethnic/genetic origin for Caucasian populations.
Originally Posted by ivan_the_terrible
They were deported along with several other northern Caucasian nationalities, though they generally get the most attention because they were the biggest.
Not sure about the Scythian connection. Seems awfully far-fetched to me, the latter being Iranic steppe-dwelling nomads and the Chechens being sedentary Caucasian highlanders.
I thought Chechens, Ossetians, Abkhaz (not sure about them), all fell under the Iranian umbrella? Maybe even Armenians?