When Usenet originated, you needed to have an Internet-connected computer. In the late 80s, this was largely limited to university campuses, which meant that the process of educating new members on the social norms already in place largely only needed to happen for a few weeks in September. In September 1993, AOL offered Usenet access to any AOL subscriber. This gave rise to the term Eternal September.
Eternal September may have come long before that. I was at Carnegie Mellon from 86-90 as a student and until 93 as an employee. It was a very big deal to Usenet when they turned on Usenet access for anyone at CMU with an andrew.cmu.edu account (a few thousand people) I think around 87. There just weren't that many people on Usenet back then, so this was a big percentage increase. Also every year (well before 93) there would be new freshmen at plenty of campuses who would get on Usenet for the first time. So you had a bunch of crunchy old neck beards who lived on Usenet, and then some clueless 17 year old kids who likely hadn't even been on a BBS prior to Usenet. The culture clash and noise was challenging.
You have to remember this was before the web. There were ways to have FTP sites or other more permanent locations to share FAQs if you knew where to look, but for the most part someone new would show up on a newsgroup and start asking the same newbie questions all over again, or hit some hot-button issue for that group and re-start an epic flame war. So each September or so would be an influx of people who didn't understand or know the culture and it was uncomfortable for all the people who had been in the club prior to that year's new kids.
Penn State (PSU) was another place that gave out Usenet access to (I assume) all students in the late 80s/early 90s. A "PSUVM.EDU" address was a big warning sign.
You didn't need to be directly connected to the internet. Dialup UUCP feeds were available starting in the late 80's. I had a UUCP feed of about a dozen groups when I was in high school, around 1992 or so. I used AmigaUUCP and dialed up to a local internet provider. I also had 4 or 5 other sites dialing into me and indirectly had a few other upstream UUCP connections. Fun times!
