http://lexicorient.com/e.o/hieroglyphs.htm

An essay (without date or authorship, but footnoted) suggests that the Egyptians borrowed the idea from the Summerians.

The Egyptians, however, did not acknowledge the borrowing from Sumerian culture. Instead, they believed that writing had been invented by their god of learning, Thoth, so they called it “words of the gods” (Warburton, 70). And since written words came from the gods, they had magical powers. By carving a person’s name on a tomb or monument, the Egyptians believed that they were helping to keep that person alive if they had passed on. Similarly, by erasing a person’s name from the inscriptions would make the person disappear. Words were so powerful that putting a written list of objects in a tomb was the same as putting the objects in themselves. Since the Egyptians believed that a person’s life was bound up in his name, the Egyptian Kings often had five names, the most important being the throne and birth names (Harris, 18).

Egyptians developed this gift from the gods into their own unique writing system, using the pictograms they borrowed from the Sumerians but drawing them in a very different style. When the Egyptians first started writing, they used simple pictures to represent objects, just as the Sumerians had. In combination, these pictures could also narrate an event.

http://www.onlineessays.com/essays/history/his172.php