(corruption of the Dutch personal name Jan Joosten, itself a shortening of Jan Joosten van Lodensteijn)
A Foreign Samurai
There were only a handful of “foreign samurai” and so Jan Joosten has a unique place in the history of foreigners in Japan.
In 1600, he arrived in Japan and was eventually made an advisor of foreigner affairs and translator for the new shōgun, Tokugawa Ieyasu, and his court at Edo Castle. He was granted permission to marry a Japanese woman and given a mansion with the inner moat of Edo Caste (丸ﾉ内). He was also given samurai rank and appointed 旗本 (hatamoto, or direct retainer of the Edo Tokugawa family).
Apparently, the dude was bitter about not being allowed to return to Holland and became a raging alcoholic and basically turned into a belligerent asshole. At some point he was refused audiences with the shōgun, Hidetada, and the retired shōgun, Ieyasu. Not sure what happened to him after that.
But his long ass Dutch name was apparently re-made into a Japanese-ish name. To the Japanese, he called himself Jan Yoosten ヤン・ヨーステン which was put into Japanese as 耶楊子 (やようす – Yayōsu). Over time the pronunciation or the kanji used to write the name of the area near his former estate changed to the present 八重洲 (Yaesu).