 In Tolkien's invented Elvish language Quenya, "Eru" means "The One", or "He that is Alone" and "Ilúvatar" signifies "Allfather".The names appear in Tolkien's work both in isolation and paired ("Eru Ilúvatar").In earlier versions of the legendarium, the name Ilúvatar meant "Father for Always" (in "The Book of Lost Tales", published as the first two volumes of "The History of Middle-earth"), then "Sky-father", but these etymologies were dropped in favour of the newer meaning in later revisions.