It is called the "Baader-Meinhof Phenomenon" or "frequency illusion".
Baader-Meinhof is the phenomenon where one happens upon some obscure piece of information-- often an unfamiliar word or name-- and soon afterwards encounters the same subject again, often repeatedly.
–"The Baader-Meinhof Phenomenon," written by Alan Bellows
Stanford linguistics professor Arnold Zwicky coined [the term "frequency illusion"] in 2006 to describe the syndrome in which a concept or thing you just found out about suddenly seems to crop up everywhere.
It’s caused, he wrote, by two psychological processes.
The first, selective attention, kicks in when you’re struck by a new word, thing, or idea; after that, you unconsciously keep an eye out for it, and as a result find it surprisingly often.
The second process, confirmation bias, reassures you that each sighting is further proof of your impression that the thing has gained overnight omnipresence.
–"There's a Name for That: The Baader-Meinhof Phenomenon," by Pacific Standard staff
"Just Between Dr. Language and I," by Arnold Zwicky on Language Log
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