Palimpsest

A palimpsest is a page that has been written on, scraped off, and used again. The word "palimpsest" comes through Greek and Latin, a two part word meaning ("again" + "I scrape"), which meant scraped (clean and used) again. It is has also been used to describe a layering of many messages with in one object or transmission. (eg. the book/movie Contact by Carl Sagan.)