Ben trovato is a common abbreviation of the Italian phrase Se non e vero, e ben trovato; 'If it is not true, it is well invented'. In this case invented means 'made up'. And so ben trovato refers to something that is worth having heard even if it's not true.
It can also mean a story or anecdote that sounds like it should be true even through its not. "The tale of George Washington and the cherry tree is ben trovato, but apocryphal."
Ben trovato is often used to mean the authority to which false stories can be attributed to, and so is both an idea and a person.