§ Orod Thon >> Orod Thuin (TI:420)
This place name appears later in Treebeard’s song as Orod-na-Thôn (LotRIII, ch.4).
Both names seem to mean *’pine-mountain’ or *’mountain of pines’ with N. orod ’mountain’ (ÓROT-). The Etymologies give N. thaun ’pine-tree’, pl. thuin (THŌN-) as an Ilkorin loan; later Noldorized S. thaun, thôn < thānı̆- or thôn ’pine’ < stŏna (RC:384, PE17:81-82). Here, Tolkien obviously decided that the word should have a short vowel o, but kept the plural thuin – compare Duil Rewinion with dol or dôl > pl. duil above (2.43).
See also Dorthonion, Dor i Thuin or Dor i thoen ’land of Pines’ (PE17:81, RC:384).