There's a good case to be made that Osiris dates as far back as early-dynastic Egypt... but nothing definitive.

"The PT, as well as the CT and other later texts, call Horus a son of Osiris-Orion and Sothis-Isis-Hathor. Osiris and Isis are not attested before Dynasty V. On the other hand, PT-371 identifies Khenti-imentiu (Foremost-of-the-Westerners), the divine patron of the royal necropolis at Abydos from the predynastic onwards, with Osiris who in turn was the god of the dead par excellence beginning in Dynasty V. Possibly Osiris was known as Khenti-imentiu as early as the beginning of Dynasty I (Wilkinson 1999, 288)." (Krauss 2010, 137)

B.A.Hokom