Etymology

Perhaps going back to Proto-Turkic *kara teŋiŕ ‎(literally “north sea; black sea”) (compare Chuvash Хура тинӗс ‎(Hura tinĕs)) or earlier (compare Mongolian Хар тэнгис ‎(Har tengis)), equivalent to kara ‎(“black; north”) +‎ deniz ‎(“sea”).