I am looking for a word or expression that means roughly "a term which is commonly thought of as understood but in reality few non-specialists really do". Sort of a linguistic urban myth. An example might be "fabric of space", which is kicked around in popular science articles and non-physicists just read on as if they know what it means, even though, if you pressed the non-physicists, they could not tell you what it is. So, I need an expression which is a little of the reverse of "hidden in plain sight." Thanks in advance for any suggestions.
A person who thinks they understand but doesn't really would be referred to as an "armchair expert" in the UK. Or a barrack room lawyer in matters legal
According to one of the scientists who has studied her bones, she is a Rosetta Stone for understanding our early evolution.