I am planning on making this thread a brief lesson about the Legendary* weapons that the Samurai Heroes have available to them throughout the life of the game. That is if I can find anything on their real world counterparts or influences. I encourage the Vikings and Knights to do the same for their Factions.
I quick disclaimer; I am not by any means a historian. I'm simply researching the names of the weapons and providing what information I can about them. Note that some will not have as significant or flashy stories with them.
FYI: A lot of these names will pop up in anime/manga series, but those will not be priorities unless I find nothing better.
Weapons in Japanese Mythology:
Kusanagi::
The Kusanagi is a Season 1 Legendary weapon set for the Orochi. It is probably one of the most famous swords in Japan, because it is both a national treasure and a cultural relic of the Shinto religion. It is one of the three Imperial Regalia of Japan, along with the Yata no Kagami (the mirror), and the Yasakani no Magatama (the jewel).
The legend behind the Kusanagi is that it belonged to the Shinto Goddess of the Heavenly Light, Amaterasu. The tale that goes with it states that Amaterasu's brother, the God of the Summer Storm, Susano'o, acquired the blade after slaying the Yamata no Orochi (Nine-Headed Serpent). He presented the sword to her as a peace offering after she cast him out of heaven. Amaterasu later on bestowed the blade onto the 12th emperor of Japan, and eventually became a regalia of the nation. A little side note, the Kusanagi has not been seen by anyone but the priests who watch over the regalia and the Imperial family, so the real Kusanagi may or may not look as it does in the above illustration.
Masamune:
The Masamune is a Season 3 weapon set for the Kensei. Another popular weapon, typically found in most Japanese influenced RPGs that have longswords or greatswords.
The Masamune is named after the famous swordsmith Goro Masamune, who is said to be one of the best in the Kamakura Period of Japan. (1288-1328) Masamune's swords were renowed for their high quality and visual beauty. There is a legend connected with Masamune and another famous swordsmith from a later era, Muramasa Sengo. The legend states (despite that they lived in different time periods) that Muramasa challenged Masamune to a test of who could produce the better sword. After placing their finest blades against the current of a small river, it showed that Muramasa had cut everything that came near it, from leaves and fish to the very air that blew around it. Whereas Masamune only cut the leaves, and let everything else pass by unscathed. A monk who saw it stated that while both blades were of great quality, Muramasa's sword was bloodthirsty, and slayed everything it came into contact with while Masamune's sword did not needlessly cut which did not deserve it. Throughout Japanese history, Muramasa's swords we seen as evil and demonic, while Masamune's were seen as holy and good.
Other:
Orochi
Okimasa
Okimasa is a Season 2 weapon set. I was not able to really find much on what this weapon's name could influenced by, however there is a swordsmith named Tsukamoto Okimasa who might have been the influence for the name.
Ippei
Ippei is a Season 2 weapon set. Ippei is a masculine Japanese name. Beyond that, there is not many famous people with the Ippei family name worth mentioning.
Toshiro
Toshiro is a Season 3 weapons set. Toshiro is another common masculine name. A personally picked person of interest with Toshiro in their name is Toshiro Masuda, who was the musical composer for the anime series Naruto, as well as a dozen other series.
Sasakura
Sasakura is a Season 3 weapon set. There is an engineering company called Sasakura Engineering (surprise!)
Tadayoshi
Tadayoshi is a Season 3 weapon set.
There was a Japanese general in feudal Japan (1337-1392) named Ashikaga Tadayoshi. The Tadayoshi was a Samurai family that had ties to the larger Minamoto clan. (Japanese clans are complex and not really easy to understand in a few hours of reading).
(More to come.)