A word appearing as an element in the Entish words Tumbalemorna “Deepvalleyblack” and Tumbaletaurëa “Deepvalleyforested” (LotR/1131), an elaboration of tumba. In Words, Phrases and Passages from the Lord of the Rings (WPP) from the late 1950s or early 1960s, Tolkien translated it as “depth, deep valley” (PE17/81). I think it means “depth” as in “a depth” rather than an abstract measure of “depth”, for which I would recommend ᴺQ. núrië.