From Tolkien Gateway
Matěj Čadil - Duilwen

The Duilwen was one of the six rivers that flowed west through Ossiriand to meet Gelion. The Duilwen was the last-but-one of these to flow into the great south-flowing river; only the Adurant was further south.[1]


Duilwen can probably be considered as a Sindarin name,[2] but was originally conceived as Ilkorin by Tolkien, consisting of the Ilkorin elements duil ("river") and gwene ("green").[3][4] Helge Fauskanger has suggested that the element -wen is a "lenited and shortened form of gwene".[5]


Seven Rivers of Ossiriand
Gelion · Ascar · Thalos · Legolin · Brilthor · Duilwen · Adurant