Nellie gets close to the origin on this one. The poem was part of a book including numerous Kipling poems, but held together by his writings about two children who learn of their local history by 'calling forth' people of other times from their locality.
The first 'person' called forth is 'Puck' who they know of from his appearance in Shakespeare's A Midsummer Night's Dream
The whole story is told in the books "Puck of Pook's Hill" and "Rewards And Fairies"
Together they form a good source of history, and folk history, for Southern England.