This is apparently what you'd ask someone in Norwegian when they are obviously feeling sad, and you want to know why they're upset. Mind you, most native English speakers would probably not use this sentence ... the English equivalent would be "Why so sad?" or, more simply put, just "What's wrong?"
According to Wikipedia (I did a quick check, to make sure I was remembering correctly) cognates are just words with a common origin, even if it's no longer obvious. Some cognates don't look alike at all, like French "père" and English "father." Though of course, the less obvious, the less useful it is to the learner.
These g/w ones are kind of exciting to me, because they look different ENOUGH that I didn't notice them at first, but once I did they were all over the place and a bunch of words suddenly became a lot easier to remember. And I guess I wanted to share, in case it helps other people too?
I can see how that would be helpful, but the problem with looking for cognates is that they also run the risk of being a false cognate, so one could remember a word wrong. Also, I've found in Norwegian that words tend to build on one another, or combine two words to make one. Therefore personally I don't look out for cognates as much, I try to see what parts of a word are present and what that could then mean.