Varro states that his teacher Aelius Stilo called this god Diovis filium, i.e. Dius Filius as the Greek Διόσκορον Castorem on the grounds of the alteration of the letters d and l in the Sabine tongue.
[8][9] The god, at some points, was certainly not a mere aspect of Jupiter but a separate entity, known in Rome for some time as Semo Sancus Dius Fidius.
[11] Dumézil underlines the peculiar intertwining and mixing of Jupiter and Dius Fidius as wardens of oaths and wielders of lightning bolts.
[14][15][16] The fact that Sancus as Jupiter is in charge of the observance of oaths, of the laws of hospitality and of loyalty (Fides) connects him with the sphere and values of sovereignty, i.e. in Dumézil's terminology, of the first function.
[citation needed] Theodor Mommsen, William Warde Fowler and Georges Dumézil among others rejected the tradition that ascribes a Sabine origin to the Roman cult of Semo Sancus Dius Fidius, partly on linguistic grounds as the theonym is Latin and no mention or evidence of a Sabine Semo is found near Rome, while the Semones are attested in Latin in the carmen Arvale.
Some aspects of Dius Fidius' oath ritual, such as requiring the open sky, the compluvium of private residences and the fact the temple of Sancus had no roof, implied to romanist O. Sacchi the idea that Dius Fidius' oath predated that for Iuppiter Lapis or Iuppiter Feretrius, and had its origin in prehistoric rituals, when the templum was in the open air and defined by natural landmarks such as the highest nearby tree.
[27][28][29] Supporting this interpretation is the explanation of the theonym Sancus as meaning sky in Sabine given by Johannes Lydus,[30] an etymology that, however, is rejected by Dumézil, Briquel and others.