Why is it called "flat assmbler"?What dose "flat" mean?

It builds the project from a hundred source files in 2 seconds flat.
Well, if being serious, I think (in my opinion), it is because it has no linker.
It is also possible, that it is 'flat' because all segment registers are set to same value, making it 'flat' memory model.
It would be interesting to hear from the creator of the Flat Assembler.

That is the reason IIRC.

It was stated here long ago, but I can't find the post right now.

There is a thread posted 20 years ago: https://board.flatassembler.net/topic.php?t=3351

A quote from someone on that thread:

"It is something like tiny mode, but with 4gb limit instead of 64kb (which ought to be enough for anyone by the way...).
This way you dont have to care with segment pointers, you don't need to maintain both FAR and NEAR pointers etc. This model was called "flat"."