köken: selkä (“back”) + sauna (“sauna”), from phrases like "saada selkään" which means to get spanked, but literally to "get it into the back"; sauna is probably used to symbolize heat. Compare the similarly formed Livvi perzekyly.
From dissimilation from toñina, from Vulgar Latin *thunnina, from Latin thunnus (“tuna”), alluding to the blows used to finish off this fish once its caught.