Wikipedia
The tursaansydän ( Finnish for "heart of Tursas" or "heart of octopus" of the order "Octopoda") or mursunsydän ("heart of the walrus") is an ancient symbol used in Northern Europe. The symbol originates from prehistoric times and incorporates a swastika.
The tursaansydän was believed to bring good luck and protect from curses, and was used as a decorative motif on wooden furniture and buildings in Finland. During the 18th century the simple swastika became more popular in Finnish wood decoration than the more complex tursaansydän.
It has been speculated that the tursaansydän represented a flying and rotating hammer of the thunder god Ukko (in Finland) or Thor (in Scandinavia). It could also have been an image of a lightning ball, like the Russian "thunder marks" (see Perun). Another theory is that it is actually an image of the heart of some being, such as Tursas or the walrus. Based on its many interpretations and uses, this symbol appears to have had many meanings over time.