"In their ancient songs, their only form of recorded history, the Germani celebrate the earth-born God Tuisto. They assign to him a son, Mannus, the author and founder of their race, and to Mannus three sons, after whom the people nearest the ocean are named Ingvaeones, those of the centre Herminones, the remainder Istvaeones. -Tacitus"
Who is this Tuisto described by the Romans to be the ancestor of the Germanic people?
If we look at the etymology of the word, we can see that Tuisto is connected to the proto-Germanic root twai which means two. Another possibility is that the name comes from the Proto-Germanic Tiwisto which is connected to tiwaz. The two main theories about the identity of Tuisto is that he is now known as Tyr or the primeval giant Ymir.
Ymir:
The theory with the most support is that Tuisto is the giant Ymir. Both are hermaphroditic beings, in Dutch it is called tweeslachtig, twee can be found in the name Tuisto. Ymir lived when our world did not exist yet. From his corpse, the world was shaped. His blood became the seas, his bones became the hills, his hair became the trees and plants and the sky was made from his skull. Ymir was the first living being and from him, the race of the Jötunn was created. This supports Tacitus's words that Tuisto created humans.
Maybe the Germanic creation story changed overtime as so many other aspects of the Germanic lore changed. Tuisto, the first being created mankind. This story might have turned into the Norse story of Ymir creating the Jötnar. What is still however a puzzle is the mention of Tuisto being an earth-God. There was no earth when Ymir lived but maybe this is just a part of the creation story that changed over time or the Romans did not write it down correctly. We can only guess.
Tiwaz:
The biggest argument against Ymir is that Tuisto was a praised God amongst the Germanic people. Ymir however wasn't, the giants are generally considered to be the enemies of the Gods. If you look at the other possible meaning of the name Tuisto, Tiwistaz, which means the most divine, it makes suddenly more sense that he might be connected to Tyr. Tyr was considered the chief God of the Germanic people until Wodan took his place, Tuisto is also named as the most important, the founder of the human race.
Maybe the Germanic people at first called him Tiwisto but languistic changes over time turned tiwisto into Twisto. Tacitus in turn might have written this name down as Tuisto. Tiwaz literally means God and Tuisto could have simply meant the most divine of the Gods. We know that Tyr is most likely related to the proto-indo European God Dyeus and we can see parallels in proto-indo European cultures of a God who created mankind through three sons. A small interesting thing about Ymir I want to add here, in the old Norse story concerning Ymir, he was slaughtered by Odin and his two brothers, three sons.
These three sons of Tuisto, refer to the people living in certain geographical regions of Germania. The Ingvaeones can be found in modern day Netherlands, Northern Germany and Denmark. The Herminones people are those of modern day east Germany, Austria, Poland, Czech. And final the Istvaeones people can be found in modern day south-Netherlands, South Germany, Belgium and parts of Northern France.
Unfortunately due to lack of archeological evidence and written down words, we do not know for certain who Tuisto was, these are all just theories.
Here are photos of Ymir and Tyr, unfortunately I do not know the artists.