:::"Da" means "large" or "great".  "Yuanshuai" is a chinese rank equivilant to a Marshal, the guy who commands all of the military branches.  So Da Yuanshuai would be like the "Grand Marshall" or something like that.  The full name was "Hailugundayuanshuai", which meant "Grand Marshall of the Army and Navy".  The rank name was changed in 1935 by the ROC government to "Tejishangjiang" which means "General Special Class", but some people translated it as "Generalissimo".  The rank is a military rank, and has nothing (theoretically speaking) to do with the civil government of the ROC.  He was President and Grand Marshall at the same time until like 1947 when the constitution was finished and implemented.  After that, he was just President.