It seems that we are still accepting questions on the history of mathematics as well as on notation. Why was this one not considered to be of research level on these two tags? I have checked the help center and can't find an answer there.
I have cast a final vote to reopen, but: I would encourage users to give History of Science and Mathematics a try in cases like this. (It is in danger of becoming moribund, which I think would be a shame, as there are real experts who have contributed there.)
Michael, if you do not receive answers that answer the question you asked to your satisfaction and in a reasonable amount of time, then please consider flagging the question to request migration to HSM. I notice that Franz Lemmermeyer, who seems to be knowledgeable about history, was one of the closers; perhaps he'd prefer to answer you there (?).