J.R.R. Tolkien’s invented ancestor-language from which Quenya and Sindarin developed is Primitive Quendian.
In Tolkien’s internal history of languages, Primitive Quendian was spoken by the first Elves after their awakening at Cuiviénen. As Elves migrated, separated, and changed their speech over long periods, the language divided into related branches.
Quenya and Sindarin ultimately belong to different later developments within that family. Primitive Quendian is therefore a linguistic reconstruction inside Tolkien’s mythology, not a language spoken by a real historical community. It is also easy to confuse with Common Eldarin, a later stage in the fictional family tree, or with Valarin, the language associated with the Valar.