Events pass into news, and then into history, and then into legend. In the process, the story changes: characters split and combine, gaining or losing attributes, and the narrative rearranges according to the needs and mores of the tellers. George Washington chops down the cherry tree and cannot tell a lie; ordinary people become heroes and villains. The fairy tales turn from cautionary instruction to fantasy. The true roots of the stories become cloudy. Myths from differing cultures seem wildly different on the surface but can be traced to a common source.
What's that process or phenomenon called? (The changing of legends over time or the academic term/analysis of differing legends with common roots, either one.) It's not memetic mutation, I know that much ... but the idea isn't all that different. Is there a specific term that would be used by an anthropologist or archeologist to describe how (possibly) real actions and events turned into our legends of Merlin and Camelot, for example?