This search led someone to my blog so I thought I’d answer it.
Lighthouse is called fyr in Swedish. Fyr means fire, but not in modern Swedish. It is part of some words other than lighthouse and in the military phrase ge fyr which means fire/shoot, as in fire at will. From German feuer, Greek pyr. Pyroman is Swedish for arsonist. Also found in the modern Swedish word fyrverkeri, literally meaning fireworks and the old Swedish word helsefyr meaning hellfire. Fyr meaning lighthouse comes from fyrbåk. Not sure what båk means, it’s not a contemporary word, but it probably means pile of wood, or rather a built structure. Bål is the word used for this today, as in a pile of wood you would burn a witch on. Båk could be connected to the English word beacon.