The kastike conspiracy

My Finnish is not as good as it should be, although I can sometimes get by in an emergency. However, I do know enough to occasionally eavesdrop on buses and trains, to find out what everyone is talking about.

It requires concentration on my part, and I have become startled to discover that many conversations that I tune into seem to involve the word 'kastike', meaning sauce or dressing for food.

So what's all this about? Either everyone in Finland is forever discussing gravy, or it's a secret code for "shut up, the foreigner's listening!"