The word sun comes from the Old English word "sunne," which derives from the Proto-Germanic word "sunnon." There are many cognates in other languages such as the Dutch word "zon" and the German "sonne," but no one knows for sure how the word came to be used. It probably derives ultimately from the Latin name for the sun, "sol."
The ancient Greeks called the sun Helios, which was also the name of their god of the sun. The Greek name is still used in words such as heliotropic and heliocentric, but the more commonly used root name for the sun is the Latin word sol, from which comes the words solar, solarium and solstice.
Given the prominence of the sun in the sky, it is not surprising that most mythologies include a sun god. The Egyptians called him Ra or Re. To the Hindus he was Surya. To the Mesopotamians he was Utu or Shamash. The Celts called him Lugh. While most mythologies pictured the sun as a masculine god, the Japanese and the Hittites worshipped female solar deities. To the Japanese she was Amaterasu, while the Hittites called her Arinna or Hebat.