Nevada survives plane and guns hits.
I didn’t know that it was rebuilt to almost a South Dakota class battleship. It also got the guns taken off Arizona. Not used to bomb Japan homeland.
http://militaryhistory.about.com/od/worldwariiwarships/p/World-War-Ii-Uss-Nevada-Bb-36_.htm
Some googling confirmed the nickname, but I couldn't find a site explaining it.
Looking up meanings for "maru" turns up only one meaning of the term that might apply - it is often attached to Japanese ship names.
During the interwar years, Nevada mostly served in the Pacific Fleet. So, I'm speculating, but the nickname may have meant the Old Ship. It certainly was that, having been laid down in 1912.