The surrounding softer rocks have been eroded over time by ice age glaciers during the Riss glaciation, creating an inverted relief and giving the mountain its present-day shape.

[1] The first written accounts of Hohentwiel Castle are held within the St. Gallen monastery chronicle of Ekkehard IV (circa A.D. 980-1060) as "castellum tuiel", which was reportedly besieged in 915.

In the Late Middle Ages, the name of the castle evolved from "Tuiel" to "Twiel" and eventually moved to its current spelling of "Hohentwiel" (lit.

Initial attempts to explain the etymology by Melchior Goldast pursued a Latin derivation of duellum meaning 'place where fighting [took place]' but this attribution was rejected by Ernst Förstemann in his Altdeutschen Namenbuch (Old German Name Book) of 1859 in favour of a Celtic conjecture.

As Hermann Jellinghaus noted upon revisiting the naming work of Förstemann in 1916, the latter suggestion was found to be "hardly Celtic", and as Twiel recurs in several areas of Switzerland, a new hypothesis was required.

The Radolfzeller Aach tributary of the Rhine runs at the base the eastern slope of Hohentwiel, while Lake Constance is located some kilometres south-east, and the town of Hilzingen 3 km west.

With the beginning of the Alpine Uplift Event, which transpired approximately 65 million years ago, land rose from the sea due to the collision between the African and European continents.

To compensate for the elevation of land, the area inbetween the newly formed Alps and Swabian Alb subsided, and with it, the Hegau region.

During the Miocene period (c. 23-5.3 million years ago), after the flood waters receded, the deep fractures and stresses caused from the uplift of the Alps and Swabian Alb resulted in intraplate volcanism.

In the first three million years, eruptions of volcanoes such as Ur-Hohentwiel reached the earth's surface, creating a tuff cone mountain which towered over its surroundings by 100-200 metres.

Originally, the Monastery of St. Georg was within the fortress, but in 1005 it was moved to Stein am Rhein (now in Switzerland), and the Swabian dukes lost control of Hohentwiel.