from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. the name of a river, lake, sea or any other body of water
From hydr- + -onym. (Wiktionary)
There are a few Scandinavian names on the map, namely creeks carrying the surnames Balto and Lindblom and perhaps the town name Moss, all named after more likely sources than an obscure hydronym.