Protogermanic

Proto-Germanic (abbreviated PGmc; German Urgermanisch; also called Common Germanic, German Gemeingermanisch) is the reconstructed proto-language of the Germanic branch of the Indo-European languages.

Proto-Germanic developed from pre-Proto-Germanic into three branches during the first half of the first millennium of the Common Era: West Germanic, East Germanic and North Germanic, which however remained in contact over a considerable time, especially the Ingvaeonic languages (including English), which arose from West Germanic dialects which remained in continued contact with North Germanic.

A defining feature of Proto-Germanic is the completion of Grimm's law, a set of sound changes that occurred between its status as a dialect of Proto-Indo-European and its gradual divergence into a separate language. As it is probable that the development of this sound shift spanned a considerable time (several centuries), Proto-Germanic cannot adequately be reconstructed as a simple node in a tree model but rather represents a phase of development that may span close to a thousand years. The end of the Common Germanic period is reached with the beginning of the Migration Period in the fourth century.

The alternative term "Germanic parent language" may be used to include a larger scope of linguistic developments, spanning the Nordic Bronze Age and Pre-Roman Iron Age in Northern Europe (second to first millennia BC) to include "Pre-Germanic" (PreGmc), "Early Proto Germanic" (EPGmc) and "Late Proto-Germanic" (LPGmc). While Proto-Germanic refers only to the most recent reconstruction of the common ancestor of Germanic languages, the Germanic parent language refers to the entire journey that the dialect of Proto-Indo-European that would become Proto-Germanic underwent through the millennia.

...
Wikipedia