Reue does not come from any proto-form beginning with D-. Reue
- which is mainly found as a hydronym - is rather related to Irish riabh "drip"
and Latin rivus "brook/stream" and comes from PIE *rei-u- "flow" (see Pokorny
under 3. er-). This was discussed by Francisco Villar in "El Teonimo Lusitano
Reve y sus Epitetos" from Die Groesseren Altkeltischen Sprachdenkmaeler, 1996,
Innsbruck.