1) I'm a sucker for random history and Prince Sado was Korean royalty, however he was mentally unstable and killed people randomly. His father, the king, was upset by this and ordered him to be sealed alive in a rice chest where he died after 8 days. He was posthumously given the title of Emperor Jangjo in 1899. His full name when translated was Prince Successor Sado Sudeok Dongyeong Hongin Gyeongji Jangryun Ryungbeom Kimyeong Changhyu Kangheon. So I kinda just sliced out the first name...
2) Chad/Sado happens to be tied for my favorite character in Bleach.