The name for a port city on the island of Tol Eressëa, so named for its nearness to Valinor (S/260). This name seems to be a compound of ava “outer” and lónë “island”.
Conceptual Development: This name first appears as ᴹQ. Avallon, another name for the island Tol Eressëa in the earliest tales of the “Fall of Númenor” from the 1930s (LR/24). The name was doubtless a deliberate allusion to the Avalon of Celtic legend. At this stage, the island was so named “for it is hard by Valinor”, so perhaps it included an abbreviation of Valinor as an element. In The Etymologies, the name appeared instead as ᴹQ. Avalóna “Outer Isle” (Ety/AWA, LONO), a compound of ᴹQ. ava “outer” and ᴹQ. lóna “island”.
In the Tolkien’s revised stories on the Fall of Númenor from the 1940s, the name ᴹQ. Avallon(de) appeared as a name of a city on Tol Eressëa (SD/399). This name was also used as a name for Valinor itself, where it was glossed “Haven of the Gods” (SD/344); in this version of the story, ancient legends confused the island of Tol Eressëa with the land of Valinor itself. The name Avallonde most likely contained the element ᴹQ. londe “haven”, and its initial element was perhaps an allusion to the Vala (or their Adûnaic name Avalô). In the Tolkien’s writings in the 1930s and 1940s, these names applied to either the island or the city, but never appeared together.
In Silmarillion revisions from the 1950s-60s, the name appeared as Avallónë in a footnote, again as a name of Tol Eressëa “signifying the isle that lies nighest unto the Valar in Valinor” (MR/175). At this stage, Tolkien seems to have changed ᴹQ. lóna to Q. lónë “island”. In the materials making up the published version of The Silmarillion, the name Avallónë was once again applied instead to the city of Tol Eressëa (S/260). It is unclear why the name’s final element wasn’t changed back to Q. londë “haven”, which would be a better fit for the name of a port city.
Avallónë place-name; haven and city on Tol Eressëa. In the Akallabêth the city is said to be so named because it is "of all cities the nearest to Valinor", but the etymology is not further explained. The Etymologies gives Avalóna "the outer isle" = Tol Eressëa (LONO, (AWA), VT45:28)