Quenya 

tumba

deep valley

tumba noun "deep valley" (Letters:308; SA:tum and TUB gives tumbo "valley, deep valley"); apparently an extended form *tumbalë in tumbalemorna "deepvalleyblack" or (according to SA:tum) "black deep valley", also tumbaletaurëa "deepvalleyforested"; see Taurelilómëa-tumbalemorna...