The swastika symbol is now irredeemably tainted by its use by the Nazis in World War II. But it is also one of the oldest symbols in the world and, for most of history, it's had entirely different meanings.
So what are the origins of the swastika, and how has its meaning changed over time?
The symbol has been known by several names. The word "swastika" — from the Sanskrit word "svastika," meaning something like "blessing" or "good fortune" — is how it's best known today. But it was a "fylfot" to the Anglo-Saxons, a "gammadion" or "tetraskelion" to the ancient Greeks, and a "hakenkreuz" (hooked cross) or "winkelkreuz" (angled cross) to Germans since the Middle Ages.
For perhaps 10,000 years, the swastika — both left-facing and right-facing versions — represented things like life, luck and well-being in many different traditions. But it underwent a chilling metamorphosis when it was adopted by the Nazis in Germany, and the swastika is now associated with the Nazi regime and atrocities of World War II.
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"It's a very old symbol," said design writer Steven Heller, author of "The Swastika: Symbol Beyond Redemption?" (Allworth, 2010). "It comes from prehistory, with different meanings in different cultures, different nations and different religions."
Symbols like the swastika are now found at ancient sites from Mesopotamia to the Americas, and it's not known how — or even if — they are related. "Even in Jewish culture, there was a swastika," Heller told Live Science.
In every case, the symbol had four legs at right angles to one another (the three-legged versions are something else), each of which led to another right angle, often ending in straight lines but sometimes in curved lines, he said.
In the ancient Germanic tradition, the symbol seems to have been associated with the god Thor, possibly because it represented his war hammer Mjölnir. And elements of it featured in the Norse runic alphabet, Heller said.
By the 19th century in German-speaking Europe, where the symbol was generally known as a "hakenkreuz," it was generally thought to represent the sun and was adopted by several ethno-nationalist or "völkisch" movements and figures, Heller said. They included individuals who championed the racialist idea that ancient Germans were descended from Indo-European "Aryans" and who claimed the swastika used in India was originally the same as the Germanic hakenkreuz.
Adolf Hitler then selected the right-facing hakenkreuz in 1920 as the central emblem on a new flag for his National Socialist German Workers Party — the "Nationalsozialistische Deutsche Arbeiterpartei," or "Nazis" for short. But the symbol wasn't called a swastika until later — the first version of Hitler's book "Mein Kampf," published in 1925, called it a hakenkreuz, Heller said.
"Even when it was adopted by the Nazis, it was not a negative symbol," Heller said. "It was a symbol of power, strength, pride … and it was a nationalist symbol in some cases, and some people think nationalism is a good thing."
While the swastika is still used for religious purposes by some cultures, it's now also linked to the Nazis. The symbol is now banned in Germany and reviled throughout Europe, Australia, New Zealand and the Americas.
But its use in many parts of the world is blameless, said Malcolm Quinn, a professor of cultural and political history at the University of the Arts London and the author of "The Swastika: Constructing the Symbol" (Routledge, 1994).
The idea that the Nazi symbol is related to the ancient swastika from India is "a false construction developed out of Indo-European language theory" in the late 19th century, he told Live Science.
That theory then formed the basis of the idea that ancient Germans were related to the "aryas," or nobles, who are said in the Sanskrit epic Rigveda to have invaded India from the north more than 3,000 years ago.
"This fantasy dovetailed nicely with European colonialism and the false belief that 'higher' races were conquerors and 'lesser' races were conquered by them," Quinn said.
The Nazis then used the symbol to promote their fascist ideology. "What Hitler wanted was to rebrand Germany through the use of the spurious idea of a conquering Aryan race, by turning the symbol of a racist party into the national symbol of Germany," Quinn said.
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Tom Metcalfe is a freelance journalist and regular Live Science contributor who is based in London in the United Kingdom. Tom writes mainly about science, space, archaeology, the Earth and the oceans. He has also written for the BBC, NBC News, National Geographic, Scientific American, Air & Space, and many others.