G
here a wild theory assuming Zoro is not the grandmaster real name :
Ushimaru has a bull on his kimono and Ushi means Bull ---> Zoro real name is Toramaru or Shitoramaru( = white tiger )
Ushimaru has a bull on his kimono and Ushi means Bull ---> Zoro real name is Toramaru or Shitoramaru( = white tiger )