Sindarin 

lô dhaer

place name. Great Fen

Name of a marsh at the junction of the rivers Ringló and Morthond meet appearing in Tolkien’s notes on “The Rivers and Beacon-hills of Gondor” (VT42/14). It was translated “Great Fen”, but the part of the paragraph where it appeared was rejected. This name is a combination of l(h)ô “fenland” and the lenited form of daer “great”.