High German consonant shift

In historical linguistics, the High German consonant shift or Second Germanic consonant shift was a phonological development (sound change) which took place in the southern parts of the West Germanic dialect continuum in several phases, probably beginning between the 3rd and 5th centuries AD, and was almost complete before the earliest written records in the High German language were made in the 9th century. The resulting language, Old High German, can neatly be contrasted with the other continental West Germanic languages, which mostly did not experience the shift, and with Old English, which was completely unaffected.