Don't you just love when you find new meanings of old words?
palimpsest: a manuscript or piece of writing material on which the original writing has been effaced to make room for later writing but of which traces remain.
Well, it can also be used to describe the way people experience time, that is, as a layering of present experiences over faded pasts.
In collage what we do is a layering process, and oftentimes we strive to show time as layers of memories. Also often collagists do physically superimpose text over faded text.
The colliding of the literal meaning with the metaphorical meaning is fittingly manifested in the use of collage.
Yes, isn't that fascinating? How the process (of layering) can come to represent a "palimpsest" of the layering of our memories and thoughts over time.
It's all just a million layers. And layers under those million layers. Infinite layers. I suppose that is why people are inexplicable and life is exciting.