Where/how do people learn about fetishes if they aren’t actively looking for info?

My (37F) boyfriend (36M) has mentioned various obscure fetishes multiple times and mostly I have never even heard of them (balloon popping, coprophagy, etc.). I am not a prude but definitely gave him the side eye about that second one and he said relax, “we’re just on different sides of the internet.”

We’ve had plenty of vulnerable discussions about kinks and what we like so I would be surprised if he was into anything I didn’t know about. But I want to know what he is doing on the internet where he finds this information because I have never come across most of this stuff in my life. Yet when he mentions it in front of guy friends, they always recognize the fetish. Is this stuff showing up on porn sites without looking for it or some other site? Is he secretly interested in something or is this just a male thing to know about? This is causing me anxiety.