The river I'm referring to is Helgeån. In older texts, it's referred to as Heligo å or "holy river", for instance chronicles about the Battle of Helgeå.
Pretty common. Many rivers in the Germanic and Celtic world have theophoric names, but the Greeks also had river gods. Actually, the practice of sacrificing in rivers goes back at least to the Bronze Age, and is widespread across Europe. River gods of course are not part of Christian belief, but in France people have been leaving offerings/depositions at rivers and particularly river springs since historic times.
Another good example is the 'Gudenå' in Northern Jutland. There's lots of Viking swords dredged up from this one, and a side river, the Illerup Å, has both a huge army equipment sacrifice and a massive human sacrifice from the Roman Iron Age.