Why are High German and Low German dialects named after geographic regions?

The terms High German and Low German are named after the major topographic regions where these dialects historically developed and are spoken.12

• High German (Hochdeutsch) refers to the dialects spoken in the mountainous, elevated regions of central and southern Germany, as well as in Austria and Switzerland. These areas are characterized by higher altitudes, which historically distinguished them from the northern territories.12
• Low German (Plattdeutsch or Niederdeutsch) refers to the dialects spoken in the lowlands of northern Germany, specifically across the North German Plain.12

The distinction between these two groups is primarily based on the High German consonant shift, a series of sound changes that occurred in the southern highlands but did not extend to the northern lowlands. While these names reflect geographic elevation, they also serve to categorize the linguistic differences that emerged as these sound shifts spread northward from the southern highlands.132