Later Iconography of "7-gods"
Originally the 7-dots probably related to the Sumerian Sebittu. Later gods included Seven (gods), the Seven, possibly referencing the Elamite god Narudu.
For '7' being the first prime number after '5', (easily represented by the 5-fingered human hand), and later associated with the Seven Sisters, or sometimes the constellation Pleiades, it became iconographic.
In ancient Egypt, the idea of '7' was associated with a person's birth. At birth, the Seven Hathors determined the fates in an individual's life.
Read more about this topic: Seven-dots Glyph