The Language Log describes the frequency illusion as a selective attention fallacy which happens when we come across a memorable word and then start seeing it everywhere (another name for the Baader-Meinhof phenomenon). There’s another side to it called the recency illusion, when we think that a word or phrase has come into use very recently, but in fact it may be much older.
It sounds fun, but can be quite counterproductive for linguists or teachers in a language classroom. I can’t but agree with the author: “Your impressions are simply not to be trusted; you have to check the facts.”
For a more humorous take on the frequency illusion, check out this recent post from the same website.