Further work on the de Castro family I research how shows that the name de Crasto and de Castro were both used by the family. Descendants of Rodrigo (also known as David Namias de Castro born 1546 Lisbon died 1627 Hamburg use both versions of the name. I have wills from National Archives in England where various de Crasto's in Holland left to children and relations in England sums and referred to these people as de Crasto alias de Castro.
It seems to me that those descendants who moved from Hamburg to Holland as de Castro's in many cases assumed the family name de Crasto and those who moved from Hamburg to England retained the de Castro.
Like wise the now de Crasto's who moved from Holland to England seem to have reverted back to de Castro.
As yet I have found no reason for this but the two versions of the name certainly seem to be Interchangeable. It could possibly be the way the name was pronounced in Amsterdam as against the way it was in Hamburg/England,
For instance Solomon de Castro of London married Rachel Bravo. Their son Isaac moved to Leghorn Italy and when he died his family moved back to England and his son Abraham moved to Amsterdam when he became a de Crasto.
If any one can explain this interchangeability I would be happy to hear your views.