What does sun begotten mean?

Begotten means created by a means of reproduction. A son is begotten when his mother is impregnated by his father. It used to be believed that sunlight could cause creatures to be reproduced without any other assistance. We see an example of this in Act II Scene 2 of William Shakespeare's play Hamlet. Hamlet says, "For if the sun breed maggots in a dead dog, being a god kissing carrion", expressing the belief that the maggots were conceived by the action of sunlight on the dead dog, not by flies who laid their eggs on it. The maggots were definitely thought to be "sun-begotten".