I don't know. Upon seeing a variable named "three", I wouldn't immediately assume it contained the literal number 3, since that would be rather pointless use of a variable. It's an odd name, but I don't think it'll be mistaken for its literal meaning.
The LaTeX source code has definitions for the constants \@ne, \tw@, \thr@@. It's a microoptimization that is useful because of the way the TeX/LaTeX parsers work. I don't understand the details, it's beyond my LaTeX wizardry.
http://tex.stackexchange.com/questions/9787/ne-tw-thr
On the other hand, I think that this kind of definitions are not useful for C.
