Malört, generally, is a variety of bäsk brännvin, which means it is a spirit that is first distilled from either potatoes or grains, and then spiced with wormwood, much like an absinthe would be. The name Malört, in fact, comes from the Swedish word for wormwood. The spirit first made its appearance in Chicago in the early 1900s, as Swedish immigrants flocked to the city and brought their favorite alcoholic beverages with them. By the time prohibition was repealed, Malört was already quite a hit in the Swedish communities along Clark street, and as the Swedish immigrants introduced the spirit to the Polish immigrants who then introduced it to others, the drink quickly gained a foothold in the culture of Chicago.
Today, Malört is still used to a similar unifying effect, largely through Chicagoans buying friends from out of town a shot of the stuff as a joke and then posting the faces they make to instagram.