I invented that!
Claiming to have originated something or “made it up” was a popular conversational device in the NYC party/club scene of the late seventies. A device for drunken conversation, it could be applied to almost anything on the spur of the moment, and was sure to get at least a polite chuckle. And someone might actually believe it (for the moment) and generate further conversation or interest. It carries some assertion of dominance.
President Trump appears to have internalized the device. Constantly surrounded by sycophants supporting his every statement, he may have come to believe his own claims after making them.