The other day I used the term confab, and the person I was talking to (50-ish, smart) had never heard the term. I know it was a buzzword in the 1980's,
It would seem it had started to die out already by the 1980s, to judge from this, though it's more popular than the unabbreviated form:
and I was amazed that she had never heard of it and doubted it was even a real word.
The flip-side of the frequency illusion is that people start off thinking the information is new.
The flip-side of that flip-side is that this seems weird to those who are already cognisant of the "new" information. For example, some people call the frequency illusion "the Baader-Meinhof Phenomenon". That seems sensible to them, but not to me, because I already knew who the Baader-Meinhof Gang were.