Incorrect, Unsound and Unplayable

The other day I was looking through Niels Jorgen Jensen, Tom Purser and Rasmus Pape's Elephant Gambit monograph when I ran into something interesting in the "Introduction" that applies equally to the Jerome Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+)

...it is evident that many openings – the Sicilian Defense, for example –  have been diffused almost beyond reasonableness. Consequently, if you play the Sicilian, as black or White, you must accept the probability that your opponent has studied the latest grandmaster variations to the beginning of the endgame.

On the other hand, if you play something off the beaten track – let's say the Elephant Gambit – you can be quite secure that your opponent has no prepared variation; quite the contrary, he will be forced to play chess on his own. This can give you a pronounced psychological advantage: your opponent is likely to be facing his first Elephant, and has studied no variations, and the only thing he might have is some vague recollection of having read that the opening is incorrect, unsound, and unplayable. He will be looking for easy refutations, and may become frustrated when he does not find them. The pressure will all be on him. After all, he will appear ridiculous if he cannot beat an "unplayable" opening.