Literally, “via Pohjanmaa/Ostrobothnia”; a phrase using Pohjanmaa (“Ostrobothnia”) as a roundabout way to refer to pohja (“bottom”).
A story regarding this phrase is that it is a reference to the Finnish Civil War (1918). To prepare for a war of independence, a few thousand supporters of the independence movement received military training in Germany. They became to be called jääkäri (“Jager”). According to the story, after the war, it became customary to propose a toast by asking "mistä jääkärit tulivat? (“Where did the Jagers come from?”)", and to this one was supposed to answer "Pohjanmaan kautta (“via Ostrobothnia”)" (as they are said to have infiltrated back to Finland via Ostrobothnia) and then the glasses were emptied to the bottom, and that over time the question has become unnecessary. However, this story may be apocryphal.