The word circular (and the German Rundschreiben/the French circulaire) conveys (at least to me) an image of a copy making the rounds of its intended readers.
Today circulars of course do not circulate (in the above sense) but each recipient gets one copy. The only exceptions that I personally encountered were some internal circulars in one state higher education ministry (where I worked as an intraoffice messenger while job hunting), i.e. a single physical office location in a very old-fashioned sort of administration where handling of paperwork was very precisely and reliably done, and a widespread practice to circulate journals in, again, a single office location (which gets the last person on the list information on the subject as of a few months ago…)
Were circulars in other cases (i.e. where people at different locations are involved) ever really circulated? Or were they always copied to the recipients, even before the advent of carbon copies made this less labour intensive in the late 19th century? I’d imagine a single copy being forwarded by mail along a list of recipients being a very unreliable process.
I know this isn’t exactly what you’re referring to, but I remember when I was a wee kid my Mom’s family had what they called a “Round Robin Letter.” This was way before e-mail or photocopies existed. Sibling A wrote a letter and mailed it to Sibling B. B read A’s letter and then added one of her own and mailed it to C. C read A and B’s letters and added one. Eventually it would make its way back to A, who took out her original letter and put in a new one to start the cycle over again. I know my Mom really looked forward to getting those letters.
The word has other connotations. British newspapers still measure their popularity in ‘circulation’ figures, the term dating to a time when they were valuable (or important) enough to not be thrown away after one person had read them.
Newspaper “circulation” has nothing to do with individual copies changing hands, either. It’s always referred to subscribers or copies sold, and is derived from the sense of “circular publications.”
There is no way to measure how many people might read a single printed copy – this is a folk etymology. Yes, printed materials circulate after they are distributed, and always have, but that’s not why circulars are called “circulars.”
Okay… but the OP’s question is about the word “circular,” (and its French and German equivalents,) and if it ever literally referred to the idea of circulating copies – so links about clandestine publishing, (while certainly interesting) aren’t really on-topic, are they?
(I’m sorry if this sounds hostile – it’s not meant to. I tried to phrase it politely and certainly don’t mean to get “all up in your grill.”)