Complex sentence: The origins of the name are unknown, probably it is of Slavic origin, in the old Slavic language the word "wolyn" meant a wetland, and in the course of the time, it was Germanised.
Split into simpler sentences: The origins of the name are unknown, although it is likely of Slavic origin. In the old Slavic language the word "wolyn" meant a wetland, and over time, it was Germanised.