A kipper is a more usually a
fillet of
smoked mackerel with its shiny skin left on. It is
smoked until its flesh is a golden brown. In
England and
Scotland, kippers are usually served with a garnish of coarsely ground
pepper. It’s a strong tasting oily fish, traditionally eaten at
breakfast. I think it goes particularly well with
scrambled eggs.
Although it’s an archaic term: when you have two fillets (i.e. both halves of the fish) that can be called a “brace of kippers”.