I think 'Rosemary' and 'Bethnal' cleverly evoke the period and place in just two words. Rosemary sounds old-fashioned; I just looked it up and it was at its most popular in the 40s.

Bethnal St conjures up the East End (to anyone who has a passing knowledge of London, anyway) so you can picture the kind of house Rosemary and her sister would have been sleeping in, and have seen the contemporary newsreels of bomb damage in the East End.