Short answers, pulled from the story.
The word Tatar first appeared in Western European languages as Tartar, a form derived from Latin or French that likely emerged from Turkish and Persian roots. The Oxford English Dictionary notes the extra r was probably due to an association with Tartarus, the underworld of Greek mythology.
Batu Khan invaded in 1223 and 1236 before the Golden Horde destroyed Volga Bulgaria. A Russian annalist recorded that in 1236 godless Tatars sacked the city of Bolgar and killed everyone from old to young while most of the Bulgar population survived and crossed to the right bank of the Volga.
In May 1944, the USSR State Defense Committee ordered total deportation of all Crimean Tatars from Crimea. Deportees were transported in cattle trains to Central Asia primarily to Uzbekistan and 46% of Crimean Tatars died during the deportation and first years of exile.
The 2010 census recorded 6,779 Siberian Tatars in Russia who occupy three distinct regions including a strip running west to east from Tobolsk to Tomsk, the Altay and its spurs, and South Yeniseisk. They originated in agglomerations of various indigenous North Asian groups which reached some degree of culture between the 4th and 5th centuries but were subdued and enslaved by Mongols.
Russia annexed the Crimean Khanate in 1783 and at least 800 thousand Tatars left Crimea due to oppression by Russian administration from that year until the beginning of the 20th century. The Crimean Khanate was formally a vassal state of the Ottoman Empire with great autonomy after 1580 before this final conquest.