The word ‘factoid’ is often used to describe a point of trivia, but that is not its true meaning – as David Marsh explains in his ‘Mind Your Language’ blog for The Guardian – with a little help from Marilyn…
‘A factoid is not a small fact. It’s a mistaken assumption repeated so often that it is believed to be true.
At least, that was the meaning ascribed to the word by Norman Mailer, who is widely credited with coining it, in his 1973 biography of Marilyn Monroe. Mailer said factoids were “facts which have no existence before appearing in a magazine or newspaper”.
You can also use factoid as an adjective, to mean “quasi-factual”, according to the Oxford English Dictionary, which adds that it is used to designate “writing (esp. journalism) which contains a mixture of fact and supposition or invention presented as accepted fact”. I like that “(esp. journalism)”.
A true factoid should sound credible, and be assumed to be true by a significant number of people (if you are the only person who believes it, it may simply be a delusion). The Washington Times defined a factoid as “something that looks like a fact, could be a fact, but in fact is not a fact”.’