In the 7th Century King Oswald of Northumbria longed for a son. Eventually his wife had a son who was named Prince Oswy after his father. However his mother dreamed that the young prince would drown on a certain day. Fearful that the dream would become true the Queen took the baby Prince south to Roseberry Topping (
NZ5712) intending to spend the day on the summit thinking there would be no water there. However the Queen felt asleep and awoke only to find the baby drowned face down in a spring a few yards below the summit. The spring is still there on the eastern flank but no more than a muddy patch. The distraught mother died soon afterwards and both were buried in a dale further south which became known as 'Oswy-by-his-mother-lay' or Osmotherley as it is known today.
Alternatively the etymology of the name Osmotherley is considered to come from Asmundrelac, recorded in 1086, Osmundelai in 1220, Osmondirlay in 1398 and Osmoderly in 1536. Asmundr is a Scandinavian personal name and leah is Scandinavian for clearing. So a difference of opinion. I know which I would prefer to believe.
For the Wikipedia article on Osmotherley see
Link
See other images of Osmotherley