Max Heuwieser writes in "The Tradition of Passau", that Sonnen received its official name somewhere between the years 1130AD and 1150AD by Baron Von Falkenstein.

Sonnen was settled in Bavaria, Passau district, at the end of a trade-route from Vienna, Austria.

The village now boasts unique natural energy systems, being nearly fully solar powered.

Due to this historical past of the Sun in the description of the coat of arms, the Sonnen municipality describes the crest in this manner: In green, a silver bar with a flying silver falcon above, and a silver horseshoe below, justifies the meaning of this emblem: The falcon is taken from the coat of arms of Baron Von Falkenstein, who exercised ruled over the Sonnen municipality during the high Middle Ages.

The green background speaks to the times before the old-growth forest landscape surrounding Sonnen was deforested.