I recently read an article about where the minhag of “Throwing coins in a well” comes from and it seems that back in the day in was a way of worship …
That does make it assur for a yid yo do?
Is it a חשש avoda Zara?
It’s not currently done for idol worship and no one who does it has any tracking of such a source, so it’s not a problem. Many of our own minhagim if tracked properly will trace back to idol worship. But it’s not a problem, since today it isn’t idol worship and hardly anyone traces it back and today it’s just a silly hanhaga.
Example…The Shintu put papers with prayers in the wall at their shrine in Tokyo. It’s also done in Turkey near Izmir at the home said to have been the house of Mary the mother of Jesus.