Sindarin 

mereth

mber

_ so that mereth became bereth, but names occurring in Tolkiens narratives (Mereth Aderthad, Merethrond) were not changed, so this revision was never fully implemented.

meren

mber

_ so that meren became beren, but names occurring in Tolkiens narratives (Mereth Aderthad, Merethrond) were not changed, so this revision was never fully implemented. (If meren were to become beren, the related word mereth ”feast” would also become bereth.)