An Etymological Dictionary of the German Language/Annotated/Burg
Burg, feminine, ‘stronghold, citadel, castle, fortified town,’ from Middle High German burc(g), Old High German burg, burug, feminine, ‘enclosed, fortified place, stronghold, castle, town.’ Compare Old Saxon burg, Dutch burg, Anglo-Saxon burh (plural byrg), English borough, bury, burrow (especially in compounds), Gothic baúrgs. In the Old Teutonic dialects Burg corresponded to the modern town. Ulfilas translated πόλις by baurgs. According to the Germania of Tacitus, the Teutons had no urbes, but their oppida were mentioned as early as Cæsar (De Bell. Gall.). With Greek πύργος, ‘tower,’ the Old Teutonic Burg accords neither in form nor meaning. The Old Teutonic word appears strangely enough in Armenian as burgu, and in Arabic as burǵ, which probably owed their immediate origin to late Latin burgus (whence the Romance words Italian borgo, French bourg, ‘market town’; so too Old Irish borg, ‘town’). In this sense the word is solely Teutonic, and belongs with Berg to an Aryan bhṛgh-, which also appears in Old Irish bri (genitive brig), ‘mountain, hill,’ but scarcely to the verbal stem of bergen. The words for ‘town’ were not formed until the separate Aryan tribes ceased their wanderings and became permanent settlers; compare also Garten.