> don't know where the i [in Hamelin] comes from in the English transliteration
Could just be that it’s a very inconvenient consonant cluster (and and a speaker of modern English will to some degree turn it into a [lən] or [lɪn], however you spell it).
"Eine andere, weniger stark vertretene Theorie besagt, dass die Hamelner Kinder einem heidnischen Sektenführer aufgesessen sein könnten, der diese zu einem religiösen Ritus in die Wälder bei Coppenbrügge geführt hat, wo sie heidnische Tänze aufführten. Dabei habe es einen Bergrutsch oder Erdfall gegeben, wodurch die meisten umgekommen seien. Noch heute lässt sich dort eine große Kuhle finden, die durch ein solches Ereignis entstanden sein könnte."
> https://de.wikipedia.org/wiki/Rattenf%C3%A4nger_von_Hameln#H...
I'll roughly translate it:
"Another, less thought after theory says, the children of Hameln got seduced by a pagan cult leader. He lead the children to the forest of Coppenbrügge for a religious ritual, where they performed pagan dances. This caused an landslide, causing most of them to die. There is, to this day, still a large pit, that could have been caused by such an event."
I go to many metal and other shows a year. A 3-day outdoor festival in the woods with hundreds of tripping manchildren moshing in the rain resulted in a very muddy shallow depression, not a landslide. I have brief cameo in the video below. Want to see a hundred hippies sitting in the mud pretending to row ancient Roman galley?
There are many theories, one of them is the Children's Crusade[0], diseases, pagan sects, but yes, the leading one is the "Ostsiedlung".
[0] https://en.wikipedia.org/wiki/Children%27s_Crusade [1] https://en.wikipedia.org/wiki/Ostsiedlung