Translations from the Elvish
Translations from the Elvish was a work written by Bilbo Baggins between T.A. 3003 and 3018, during his stay in Rivendell, using both written sources found there, and interviewing the Eldar he met there.
This work "of great skill and learning" filled three volumes of red leather and concerned the Elder Days. Possibly it included such works as the Quenta Silmarillion, Ainulindalë, and the Valaquenta. Thus it is speculated by some readers that The Silmarillion was a translation of it.
Bilbo gave the volumes to Frodo Baggins as a parting gift. These were later annexed to his diary, and the account of the War of the Ring, and (appended with a fifth volume later) formed the Red Book of Westmarch.
As these were used little by Frodo, and most copies of the Red Book involved mainly the first volume, the Translations were omitted from other versions. They were preserved only in the Thain's Book, and its copy made by Findegil in Gondor.