The capital city of Númenor. Tolkien glossed this name as the “City of the Kings” (UT/165), but the elements of the name appear to be ar- “noble”, menel “heavens” and the suffixal form -os of osto “city”. As such, its literal meaning seems to be “✱Noble Heaven City”, probably a reference to its location on the slopes of the mountain Meneltarma. The city’s Adûnaic name, Arminalêth, has a similar meaning.
Conceptual development: In the earliest stories of Númenor, the name of this city was given as ᴹQ. Númenos or Númar (LR/14). In the later versions of the story associated with “The Notion Club Papers”, its Quenya name was change to ᴹQ. Antirion (SD/347), but for the most part it was referred to by its Adûnaic name Arminalêth. In the drafts of the Akallebêth the Quenya name was Q. Tar Calimos (PM/145) before it was replaced by its final form Armenelos as in the published version of The Silmarillion.
In the index of Sauron Defeated, Christopher Tolkien incorrectly wrote that Armenelos replaced the name Arminalêth (SDI2/Arminalêth). He corrected this mistake on PM/145, where J.R.R. Tolkien’s notes clearly indicate that Armenelos was the Eldarin [Quenya] name of the city, coexisting with its Adûnaic name Arminalêth.
Armenelos place-name, City of the Kings in Númenor (ar-menel-os(to) "royal-heaven-city"???) The stem should possibly be *Armenelost- (compare Mandos, Mandost-).