An Etymological Dictionary of the German Language/Annotated/Pforte
Pforte, feminine, ‘door, gate, portal,’ from the equivalent Middle High German pforte, Old High German (Franconian) pforta, feminine; borrowed in the Old High German period, in the 8th century, from Latin porta; hence the absence of the permutation of t to z, which had been accomplished even in the 7th century (it is seen in Old High German pforzih, Middle High German pforzich, from Latin porticus, which was introduced in the 5th or 6th century with the Southern art of building in stone; compare Anglo-Saxon portič, English porch). In Middle German and Lower Rhenish, in which the permutation of t to z did not take place until later, we find in the Middle High German period the permutated form porze. Modern High German Porte, Middle High German porte, Old High German (Upper German) porta, is due to a more recent introduction into Upper German.