.... the early 1800's British sailing ships because the desert looked like, well ... an unhealthy male part.
Here is some google info on it: The word "dick" has appeared in any number of strange places. Around the 1840s, "dick" was used to mean a type of hard cheese; when treacle sauce was added, it became "treacle dick", and finally when currants or raisins were added (looking like little spots), the "spotted dick" was born.
The earliest recipes for spotted dick are from 1847. For non-British readers, "spotted dick" is a boiled suet pudding, with bits of dried fruit (usually raisins or currants) that (as already noted) look like little spots.
The Oxford Companion to Food comments that, strictly speaking, "spotted dick" is made by taking a flat sheet, spreading sugar and raisins on it, then rolling it up. A similar dessert is "spotted dog," a plain cylinder of suet paste with the raisins and currants and sugar stuck into it, so that the spots are visible on the outside. Both spotted dick and spotted dog were traditionally boiled (or even steamed) in a cloth, but nowadays they are usually baked.
As bad as it sounds, it is a really great tasting desert. Most all the small town pubs have it listed on their chalkboard menus.