Telerin evolved directly from Common Telerin, the primordial tongue of the Teleri or Lindar, a clan of the Elves. During the Great Journey it diverged from Common Eldarin, which itself was descended from Primitive Quendian, the original language of all Quendi, or Elves.
The language of the Teleri of Valinor was influenced by and in turn influenced Noldorin Quenya, and these languages remained very closely related. One Telerin change was from Common Eldarin /*kw/ to /p/; this parallels a real-life change in Brythonic Celtic languages, including Welsh, which has similarities to and may have been an inspiration for Sindarin (see Q-Celtic (Goidelic) and P-Celtic (Brythonic).
Telerin is the tongue of the Teleri who reached the Undying Lands, also called Lindalambë (tongue of the Lindar).
Telerin was considered by some to be a dialect of Quenya, but the Teleri themselves considered it to be an independent language. It was much more conservative than Quenya, and was the closest to Common Telerin (from which Sindarin and Nandorin were also derived), and even to Common Eldarin of the later Elvish languages.