Sir William Boswell, seventeenth-century diplomat, was a powerful, intriguing figure. There is not much about his family or where he came from, although there is plenty of historical evidence about his political activities. But who was he? Apparently he "claimed affinity" with his wife's family, the Bosvilles of Kent. As Alan Stewart puts it in the DNB, Boswell "married his cousin Margaret Boswell or Bosvile, a relation of Sir Ralph Bosvile of Eynsford in Kent."
In this post I'll suggest that William Boswell's family was actually from Durham. He probably was not related to Margaret Bosville, although certainly their names were spelled similarly.
We can see that Boswell's family was from Durham from the will of his father, John, who died in 1595--the reference for the will is given in History of Parliament online and in the DNB article by Alan Stewart.
The will of John Bowswell, of Suffolk, is fairly detailed. In particular, it mentions that the property that John Bowswell has got from Sir Robert Gardener, in Suffolk, is bequeathed to his eldest son William Bowswell (that is, Sir William Boswell). However, later in the will, John Bowswell names his brother Thomas as the heir of all his property in Barnard Castle village in Durham. The will refers to his right to hold the land "of one John Fulthorpe esquire and his ancesters ... many yeeres beyond the meamory of man"; a few lines later John refers to his father, "deceased of the heires of the said John Ffulthorpe."
Barnard Castle in Durham has a long association with the Bowes family, and there is a village called Bowes in Barnard Castle. George Bowes notoriously executed the northern rebels and took possession of Streatlam Castle in Durham in 1569. The Fulthorpes and the Bowes certainly had their links to each other: Anne Fulthorpe’s son married Sir George Bowes’ daughter, establishing family links between Bowes and Fulthorpe several decades before John Bowswell died in 1595. Bowes sounds a lot like Bowswell. You can see where I'm going with this. Perhaps Boswell is not a corruption of Bosville after all, but instead a corruption of Bowes.