Shechita is a made up word.

The first Mishna (law) in the Talmudic tractate (book) called Chullin, states that any Jew may slaughter meat for the Jewish people. In recent centuries, however, because not everyone is versed in the details of how to perform the shechita (slaughtering), those who wish to slaughter are required to gain a certificate indicating that they know the laws well.

While Genghis Khan was exceedingly violent and certainly did kill Jews, he did not take any specific action to target Jews for death. He pillaged, burned, and murdered millions of whom some were Jews. The only serious action that Genghis Khan took against the Jews (and Muslims as well) was to ban ritual slaughter practices of shechita (and dhabiha in the Islamic case).

In order for a land animal to be kosher it must have a cleft hoof and chew its cud. A bison fills both requisite conditions, so it is considered kosher.

Of course, in order for bison meat to remain kosher, it must be slaughtered according to the rules of Shechita or Jewish Ritual Slaughter and must not come into contact with dairy products or treif (non-kosher) products.