Proto Language
Definition - (Aka Ursprache)

A hypothetical parent language from which a language family's languages and dialects have been derived.

Example -
Proto-Indo-European, Proto-Bantu, and Proto-Uralic.

Etymology -
The word was coined by combining the combining form proto- with the word language.

Oxford English Dictionary -
It first citation is from 1948:
"Our reconstruction of a proto-language is theoretical and partial."
(W. F. Twaddell in Language XXIV. 139)

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