Dear Mr. Amos,
I agree with your skepticism about frequency of name changes. My
experience of several decades tells me they are rare, but usually for
very good reason. I presume your thinking the name was Hammonds in
the 1871 census was that you find the family at the same address as in
1881 or that you find the family with the same given names, but with
the surname Hammonds. Depending on how certain you are of this would
determine how strongly you search for the family under each surname in
the previous generations.
Could you tell us what that evidence is?
IF it were the same family, I'd initially suspect a son born out of
wedlock by a mother named Hammonds, later taking the surname of his
biological OR adopted father for various reasons. Or because of
inheritance where his assuming the surname Amos would provide
inheritance to some fortune of a grandparent. Was the family affluent?
Depending on the age of William Amos, you might be successful in
searching for his birth or marriage record under either 'Amos' or
'Hammonds', beginning in Tredegar.
I'd much appreciate your keeping us informed as you pursue this
interesting question.
Thomas Roderick
Bar Harbor, Maine, USA