Somewhat archaic Norwegian idiom which means to stop by someone's house very briefly.
Back when rural houses in Norway were heated by burning wood or coal, keeping the fire in the stove from going out was as important as making sure a fuse doesn't blow is now. Many houses had inadequate insulation, and a cold house with little insulation required largish amounts of wood or coal to heat up. Keeping the house (and indeed the stove itself) from getting cold meant spending less wood. Spending less wood meant spending less summer time in the forest hewing it.
When residents turned in for the night the fire was left to smolder. If the stove was any good, you could count on there still being a couple of embers at sparrow fart. This, of course, made the morning ritual a little less cumbersome, since all you had to do was put in a handful of dried bark (birch bark, often), breathe it along and have a fire going in short order.
Enter the good neighbour whose fire had gone out. He'd enter the house in a hurried fashion, present his important errand, stick his spade in the stove and take some of your smoldering charcoal over to his house. All this - hopefully - before his stove cooled too much.
- Was that Sverre? What was the rush?
- Nah. He was just over to fetch heat.