Parkin is a kind of cake made principally from oatmeal and treacle (noting that Treacle Is Not Golden Syrup!). I'm told it's this way because oatmeal has traditionally been an inexpensive variety of cereal, and treacle was likewise cheap, being essentially the waste product from the sugar refining process. It's traditionally associated with November 5th although it's good Winter warming food at any time (in fact I'm not quite sure what's so wrong with it in Summer, though I don't think anyone sells it then).
A couple of things come across when searching for parkin on the web. Firstly, many references describe it as a kind of gingerbread. I had never made the connection as it doesn't seem anything like gingerbread. It does contain ginger, but that merely enhances the flavour rather than making it taste of ginger (it actually tastes of treacle). And besides, gingerbread to me means `gingerbread men' which are biscuits, and parkin is cake. Secondly, many of the references seem to describe it as Yorkshire parkin (including the one in the back of Counting on an Elephant) which is odd as I come from Lancashire and it seems to be well known there. One reference has both Lancashire and Yorkshire parkin recipes, though if this recipe is the one my Mum tried when she said it ended up almost as heavy as lead, I'm not surprised (try adding up the weights of the raw ingredients)! Another reference contradicts this first one by saying that Lancashire parkin contains more flour than oatmeal (the aforementioned recipe doesn't contain any flour at all).
It's also clear that there are any number of variants. Some recipes use golden syrup instead of treacle, which seems to me to be missing the point. But hey, it takes all sorts. . .