Short answers, pulled from the story.
The word Cossack first appeared in written records within the Codex Cumanicus during the 13th century. Max Vasmer's etymological dictionary traces this name to a Tatar Turkic root meaning free man or conqueror.
Dmytro Vyshnevetsky built a fortress on Little Khortytsia island in 1552 to create the first recorded Sich prototype below the Dnieper Rapids. Catherine II destroyed the Lower Dnieper Zaporozhian Host in 1775 after Yemelyan Pugachev's Rebellion involved some of its members.
Stepan Razin organized his rebellion in 1667 leading Cossacks to plunder Persian cities on the Caspian Sea before returning home rich with goods. Elite elders eventually complied with the government in 1671 to receive subsidies and handed Razin over for execution in Moscow.
Approximately three thousand two hundred Cossacks from Don Kuban and Terek Hosts were stationed in Petrograd when disorder broke out on the 8th of March 1917. Their general defection on March 10 enthused crowds and stunned remaining loyal units within the capital.
The Soviet Union enacted a law in 1988 permitting re-establishment of former Cossack hosts and formation of new ones during Perestroika. Descendants began reviving their horse-centered way of life and historic traditions throughout the late 1980s.