I recently watched a Japanese drama titled 「おせん」. The title comes from the first name of the main character - the character's name is 半田{はんだ}仙{せん} who is a young お上{かみ} of a traditional restaurant.
My question is: is it common for the honorific お prefix (I guess it is used like that) to be added to names? How is it used? Other people in the drama often address this character as おせんさん. Is it normal to add both お and さん?
It was a common practice during the Edo and Meiji periods and on through Taishou and early Shouwa periods.
Women's names back then tended to be short (mostly two-syllable long and sometimes just one as OP's example) and surprisingly simple compared to their present-day counterparts. Baby girls were often named literally after simple plant, flower and animal names, such as まつ(pine)、きく(crysanthemum)、うめ(plum)、とら(tiger)、かめ(turtle)、たつ(dragon), etc. They were by and large written in kana as well because people selected these names for their sounds, not for their meanings.
These names just sounded "better", "cuter" and/or "more rhythmical" if the honorific 「お」 was added. This 「お」 was for expressing affection, not necessarily respect.
「さん」 was also added depending on who was addressing (or referring to) whom.
