I don't know if you will read this, but I am now looking up my grandfather.
He was Peter Paul Chapman, but his birth certificate says Peter JACKMAN (born 1900, son of Mary Furlong and Patrick Chapman/Jackman). I did not know, until reading this, that Jackman and Chapman were interchageable. Do you have information on that? I am trying to get my Irish citizenship and I want to show them that the names are interchangeable.