Cossacks - one of selfnames of Ukrainian, Russian and other Eurasian people of different origin. The selfname "Cossack" means simply "free man" or "free man by the will of God". During the course of time most of Slavic-speaking Cossacks became Orthodox Christians, which defined themselves as warriors of Christ, people going after the Christ and so on.
God save cossacks! Praise be free Ukraine and saint Rus!