Francis Hyde, in his book on the History of Wolverton, hazarded a guess that it may have originated as "Fowler's Slade".
Who knows?, but I have just come across a reference in the Wolverton Manorial documents that may shine a little light on the name's origin.
from half acre in Fuleweelslade next land of Thomas the clerk and from William FuleThe document dates from between 1235 and 1270 - mid-13th century. It may suggest that William Full or one of his ancestors gave their name to the slade. The slade is a green area of land often surrounded by woods. It is usually rendered in dictionaries as "greensward" but even that word has no currency these days.
If we separate the word Fuleweelslade to Fule, Weel and Slade we can probably understand the composite.
Fule, after the Full family
Weel, meaning well or good
Slade - as described aboveThus, Full's good slade.
In time Full's well slade would have modified through usage to Fuller's Slade, having only a tenuous connection with its origin and having lost any semblance of meaning.
This is merely my speculation, but at the moment the theory looks attractive.