The band uses either Cyrillic «Чорторий» or Latin «Chortoryi» simultaneously, depending on the region. Both are correct.
As for the meaning of Chortoryi, the word stands for the big whirlpool with the Chort (meaning “devil” in Ukrainian) as a root word.
Also, Chortoryi is an anabranch of Dnipro river, located in the middle of Kyiv, near the place where the idea to create this namesake project was born.