[egypturnash]

I would submit that the most prominent use of "flatland" is probably the book of the same name. http://en.wikipedia.org/wiki/Flatland

[nchlswu]

ah. I had no clue that's where it originated from. thank you for pointing that out!

I can still say that Tufte was probably the most prominent to use it in a design sense (but I'm probably wrong about that as well..)