The frequency illusion, that you learn of a word or concept and suddenly it seems to be everywhere and it wasn't before you learned about it, is apparently also known as the Baader-Meinhof Phenomenon.

https://www.damninteresting.com/the-baader-meinhof-phenomenon/

Until now, I was very familiar with the experience, but didn't know of either term for it. I expect to see it mentioned more in the future.

Also, I struggle to think of a time when I didn't know about the Baader-Meinhof Gang! Or Rote Armee Fraktion, as they referred to themselves. Or rather, I struggle to think of a distinct point where I learned about them. Some time between the 80s when I knew nothing and my late teens when I knew everything. ;-)