Quenya 

Mindolluin

blue tower

Mindolluin noun *"Blue Tower" (mindon + luin), name of a mountain. (Christopher Tolkien translates the name as "Towering Blue-head" in the Silmarillion Index, but this seems to be based on the questionable assumption that it includes the Sindarin element dol "head, hill". Unless this translation is given in his father's papers, the name is better explained as a Quenya compound.)

Sindarin 

Mindolluin

noun. pale, #blue hill

mindon (“isolated hill”) + luin (#Dor. “pale, #blue”)

Sindarin [Tolkiendil] Group: Tolkiendil Compound Sindarin Names. Published by

mindolluin

place name. Towering Blue-head

The mountain on which Minas Tirith was built (LotR/751), translated “Towering Blue-head” in Tolkien’s “Unfinished Index” of The Lord of the Rings (RC/439). It is a combination of a shortened or root form of minas “tower” with dol(l) “head” and luin “blue” (SA/minas, dol, luin).

Conceptual Development: In Lord of the Rings drafts from the 1940s, this name first appeared as N. Tor-dilluin, perhaps beginning with N. taur “high” (as suggested by Roman Rausch, EE/3.6), but it was soon revised to N. Mindolluin (WR/80).

Elements

WordGloss
minas“tower, fort, city (with a citadel and central watch tower)”
dol(l)“head, hill”
luin“blue”
Sindarin [LotRI/Mindolluin; LotRI/Mount Mindolluin; PMI/Mindolluin; RC/439; SA/dol; SA/luin; SA/minas; SI/Mindolluin] Group: Eldamo. Published by

Noldorin 

mindolluin

place name. Mindolluin

Element in

Noldorin [PE22/126; SDI1/Mindolluin; TI/310; TII/Mindolluin; WR/080; WRI/Mindolluin; WRI/Tor-dilluin] Group: Eldamo. Published by