Or, could it be a reference to "Danish caper sauce" used in traditional Viking fish recipes?

"The caper is actually the unopened bud of the caper bush, a spiny perennial shrub that reaches a height of 1 metre or more. It grows on dry stony ground in warm climates, and is found in olive-growing regions, particularly the Mediterranean. The buds are picked by hand, with the youngest, smallest ones being the most highly-prized. They are then pickled in vinegar or preserved in salt. Capers' particular pungency comes from the mustard oil they contain, and curing helps bring out their piquant flavour. They are graded according to size, the smallest being "nonpareilles," followed by "surfines," and then the larger and less valuable "capucines" and "communes."

http://www.theworldwidegourmet.com/vegetables/general/capers.htm

I used to know a fellow who treated himself every now and again to a breakfast of fried "capers" [which were actually herring, I think].