proto-language

noun2

1. •
   A language which is reconstructed by examining similarities in existing languages in order to deduce the form and aspects of a common ancestor language that is no longer known.

   • Just as Greek and Sanskrit reflect a proto-language, so do the Cypria and the Mahābhārata reflect a proto-story. — 2025
2. •
   The early utterances produced by an infant before it acquires a true language.