A silly question, my google-fu is failing me, I know that the csc.exe is the command line compiler, but I am curious what the letters csc are an acronym of?
It seems sort of reasonable to assume that it stands for C Sharp Compiler: you can't put # in a filename (and it looks odd in an acronym anyway) so csc is the closest possible thing.
A quick Google search tells me this book agrees with me.