As immortal spiritual beings, the Valar have the ability to communicate through thought, with no need for a spoken language, but it appears that it was adopted as part of their assumption of physical, humanlike forms.
[T 3] The Valar as spiritual immortal beings have the ability to communicate through thought and have no need for a spoken language, but it appears that Valarin develops because of their assumption of physical, humanlike (or elf-like) forms.
[1] According to the earlier conception set forth in Tolkien's sociolinguistic text, the Lhammas, the Valarin language family is subdivided into Oromëan, the Dwarves' Khuzdul (Aulëan), and Melkor's Black Speech.
His biographer John Garth comments that while Rúmil's lack of omniscience might seem convenient, saving Tolkien from having to work on Valarin in any detail, "the unknown is essential to the legendarium, part of the illusion of depth so vital to its aura of authenticity.
The linguist Helge Fauskanger notes that the exact structure of the endings for these verb forms cannot be determined from this limited evidence.