The Lhammas is the Account of Tongues by Pengolodh. This is a relatively early work, that shows JRRT's conception of the origin and historical developement of various languages during the 30s.
One major change between these earlier conceptions and the one that came about in the 50s, is the very origin of the elvish tongues. Here in Lhammas, they are derived from the language of the Valar which was taught to the early elves by Oromė, whereas later JRRT decided the elves created their own tongue. The art of language is said in Dangweth Pengološ to be the oldest and most beloved of the Eldar.
The Lhammas is found in three versions in HoMeV.