I’m not sure what you’re trying to find out but, to clarify, nobody changes their name ‘by deed poll’. The deed poll is simply a written record that they have done so, and deed polls only represent a relatively small number of name changes made. Before the modern era, most people could change their names as and when and however they wished to (other than for fraudulent purposes). Many changes of Germanic names around the WW2 period were simple anglicisations, so if you are searching indexes for this surname you might also want to try ‘Youngblood’?There’s a useful research guide about name changes here ...https://www.nationalarchives.gov.uk/help-with-your-research/research-guides/changes-of-name/
