Amongst thousands of other possible meaning of this acronym :
http://en.wikipedia.org/wiki/RMS
by the way RMS are the initials of Richard Stallman (Richard Matthew Stallman) too.
RMS can mean "roots mean square" when talking about the power of an amplificator (100 watts RMS for example),
and so on ...
Don't stay focused on a ship that sank one century ago, things have changed since then :-)