Avalon In The Galactic Milieu

"His former First Deputy, Catriona Chisholm, was transferred to the populous cosmop planet Avalon, where she became Deputy to Usha Singh."
-Julian May, Diamond Mask (London, 1995), 22, p. 410.

So is that a tribute to the planet Avalon in Poul Anderson's Domain of Ythri or just to the island of Avalon in Arthurian legend? See the image and here, where CS Lewis tells us that Arthur is in "'...the House of Kings in the cup-shaped land of Abhalljin...'"

Lewis also tells us:

"'Where Arthur is, we know.'
"'Where?' said Camilla.
"'In the Third Heaven, in Perelandra. In Apphalljin, the distant island...'"
-CS Lewis, That Hideous Strength IN Lewis, The Cosmic Trilogy (London, 1990), pp. 349-753 AT Chapter 17, 4, p. 738.

Names of planets link hard sf to myth and fantasy, e.g.:

Nerthus is a deity in Poul Anderson's Time Patrol series and a planet in his Psychotechnic History;

important planets in Anderson's Technic History are called Hermes, Woden, Satan, Aeneas and Dido.