In Egyptian mythology, Aker or Akar was one of the earliest gods worshipped and was the deification of the horizon. There are many indications that Aker was worshipped before other known Egyptian gods of Earth, such as Geb. Aker means "One who" curves because it was perceived that the horizonbends all around us. The pyramid texts make a(n) statement that the Akeru "Those of the horizon" (The plural of Aker) will not seize the pharaoh, with the power of Egyptian pharaoh over the surrounding non-Egyptian peoples.
As the horizon, Aker was also seen as a symbolic of the borders between the days, and so origionallt depicted as a strip of land or horizion with a head on the end of each side (A symbol of borders). Since the sun reaches it's summit in the zodiac of Leo, the heads were depicted as that of a lion. Later on the heads became full figures of lions one (Sef) repersents yesterday and the other (Duau) repersents tommorow