Today's quoted passage from THE GLASTONBURY ROMANCE (1933) by John Cowper Powys. Perhaps he thought the word 'Esplumoir' was not in Malory because he misspelt it as 'Esplumeoir'!
"As all Merlin's disciples well know, there is a mysterious word used in the Grail Books about his final disappearance. This is the word 'Esplumeoir.' It is inevitable from the context to interpret this as some 'Great Good Place', some mystic Fourth Dimension, or Nirvanic apotheosis, into which the magician deliberately sank, or rose; thus committing a sort of inspired suicide, a mysterious dying in order to live more fully. As he sought for one of his favourite passages -- for 'Esplumeoir' does not appear in Malory -- he kept murmuring that particular invocation under his breath, pondering intently on the occult escape offered by this runic clue from all the pain of the world, an escape so strangely handed down from far-off centuries in these thaumaturgic syllables."