It belongs to the Twa Sisters family (Child 10). There's a lot of related information in the Forum, but the search engine is broken at the moment. Fortunately, most of the DT files and Forum discussions have had lists of links to (most of) the others added. You may as well start with

Lyr Req: bows of london

It's a very short thread, but working through the links will give you more background information than you ever wanted, I should think. Don't believe everything that people say though; we've had some quite odd ideas come up from time to time. The refrain, by the way, is one of many different ones and is probably of very little significance.