The Name Northumley

[Guest Lakin]

I was talking to someone who lives on mortomley lane high green. He said is land was given a name called northumley. After doing some research i found some information. I don't know how true some of it is so hear goes.
Kingdom of Northumbria. King of Wessex in 802. looks like nicolas de mortumley was part of the crown & land in will or deed was given to him in the 1300s. This area was under Northumbria in the 600's to 952. after this date it came under York. After a battle.
Mortomley near to Chapeltown on the north-west,has a history which goes back to 1227. :It is mentioned among the estates of Lord Furnival in 1365 and again among those of William de Furnival in 1365 as yielding 50s per annum In both cases it is spelt Northumley.
How did this name come about.