Properly Wemba-leah, the forest clearing named after a Middle-Saxon chap called Wemba, an orignal boy from Brent who has since disappeared into the mists of time, but presumably by contributing in some way to the removal of a few trees, made space for the hallowed turf.
The village name first appears in a charter of 841. Æthelwulf was then King of Wessex and it would be thirty years before Alfred the Great would take on the task of forming England as a proper political entity.
Wembaleah was in the province of Middleseaxan, which had been part of the East Saxon kingdom — Essex — on the other side of the Romans' Watling Street (Edgware Road), which from 825 was held by a 'Dux' subservient to Wessex.
Today Brent is the most diverse county in the UK by country of birth.