The English ‘water finch’ no longer exists as a genus in modern ornithology. The bird is is defined in the OED as ‘a songbird of the family Fringillida’ (sub water n.), while the MED does not provide any definition (sub water n.)

The etymology of second half of the word, -vole, remains unclear, but may find its analogy in similar names for birds or flying creatures: palevole and pievol. An association with the word vol¹ (‘flight’ or ‘wings’) seems one possible explanation.