This question gets asked a lot, so here you go.
SUSE Linux (and the company that maintains it) has been known as "SuSE" and "S.u.S.E.". It originally stood for
"System und Software Entwicklung", which is German for "System and Software Development".
Now the company is known as "SUSE LINUX AG", and the distribution is known as "SUSE" Linux. The current speculation is that "SUSE" doesn't stand for anything anymore, it is just a name.