'Did the Celtic Saints forcibly shut down the trade by "killing" the dragons?'
They got rid of them in Ireland. At least St Patrick did. If we accept that dragons are also worms or wyrms as in the laidlie wyrm etc. Big snakes breathing fire.
'The Latin word draco, as in the constellation, Draco, comes directly from Greek δράκων, (drákōn, gazer). The word for dragon in Germanic mythology and its descendants is worm (Old English: wyrm, Old High German: wurm, Old Norse: ormr), meaning snake or serpent. In Old English, wyrm means "serpent", and draca means "dragon". Finnish lohikäärme directly translated means "salmon-snake", but the word lohi- was originally louhi- meaning crags or rocks, a "mountain snake".[citation needed] The prefix lohi- in lohikäärme is also thought to derive from the ancient Norse word lógi, meaning "fire", as in Finnish mythology there are also references to "tulikäärme" meaning fire-snake, or fire-serpent.'
https://en.wikipedia.org/wiki/European_dragonIt's perhaps interesting that the Norse is 'ormr'. From which Great Orme in north Wales is named.
According to wiki it was called that by the Vikings but not by the locals for obvious reasons. It was called orme because apparently it looks like a serpent when coming from the sea. This name took root with the growth of tourism in recent years.
However the article goes on to tell us that there have been copper mines there since the bronze age.
'Large-scale human activity on the Great Orme began in Bronze Age with the opening of several copper mines. These were abandoned around 600 BC. Excavations show evidence that the Romans reopened the workings. In 1692 mining resumed again on the Orme. Ore was extracted until the end of the 19th century. It is likely that copper from the mine was exported to Continental Europe in the Bronze Age and Roman era. In addition to the three main mining areas, there are many open-cast bell pit mines along the lines of the main geological faults.'
https://en.wikipedia.org/wiki/Great_OrmeSo it could be that the Vikings were also referring to the smelting of the ore (oh dear not another ambiguous word?).
I wonder if Herm and Hermes are also connected?