I think this is known as https://en.wikipedia.org/wiki/Cryptomnesia https://en.wikipedia.org/wiki/Cryptomnesia Paul McCartney dreamt the melody for 'Yesterday'

I think this is known as https://en.wikipedia.org/wiki/Cryptomnesia https://en.wikipedia.org/wiki/Cryptomnesia Paul McCartney dreamt the melody for 'Yesterday'. He was sure he'd heard it before, so he went around for weeks humming the tune to people, before deciding it was original. (I just found this story in my swipe file!)