Locks from Paris - how did it happen?

I have never been to Paris, and in all honesty, I don’t plan on going.But technically, I have been to Parisian soil, at the airport, though. Does that count?! LOLAnyway, even though I have never been there, the thousands of locks on a bridge (example), are quite well know all over the world. Till today, I don’t get why fixing a lock on a bridge will mean anything. Or that any wish will become true. Or that your feelings will be “forever”….Might be just my skeptical side being a bit prominent.Also thought that maybe it was some kind of tradition linked to Paris, with a background story that I have yet to find.Surprise to me, I have found some locks, on what I believe to be a sewer lid, in Portugal.The location is very nice as well, to me, nicer than Paris (no offense), but totally random.It made me wonder:– was this imported by some tourists, that thought “oh wait, here’s some metal part, let’s fix a lock here, like in Paris!”– some Portuguese people thought “why not a bit of Paris over here?”Not that it bothers me, on the contrary, found it quite amusing. But, the question remains; why to fix a lock?What is the point?Has anyone ever done such thing?I would be glad to know what were the reasons.