⋄ Mount Tor-dilluin >> Mount Mindolluin (WR:77, 80)
This is the mountain at whose foot Minas Tirith was built.
Tor-dilluin probably contains N. taur ’vast, mighty, overwhelming, awful – also high, sublime’ (TUR-), shortened to tor- in the compound. The second part can be interpreted as lenited tilluin, iteslf consisting out of N. till, tild ’horn’ (TIL-) or S. til ’point, horn’ (Silm.index), S. till ’tine, spike, point’ (PE17:36) – frequent in mountain-names – and S. luin ’blue’ (Silm.index). Thus altogether it may mean *’Mighty Bluehorn’.
Mindolluin is translated as ’Towering blue-head’ (RC:439) in the unfinished index and might contain mindon ’tower’ (MINI-) at the first glance, but The Silmarillion index states that it contains dol ’head; often applied to hills and mountains’ and #min- which occurs in other words referring to isolated, prominent, things, thus #mindol *’isolated, prominent mountain’.