One of the big downsides of the internet is the cold water it constantly pours on my idea of my own originality. Every time I think of a great idea I find someone else has already thought of it
That does not make it a etter or worse idea though. Realistically, most people will only ever have ideas that someone else somewhere else will already have had.
Does that mean, that the idea is commonly known? Not necessarily.
It is also still an original idea in terms of you having thought, that was not easily derived from what you know (but probably somehow derived, like all thought likely is).
(well, almost every time)