What is the significance of the name "Adoni Tzedek"?
Radak: All kings of Yerushalayim were called Malki Tzedek or Adoni Tzedek, like we find "Malki Tzedek Melech Shalem" (Bereishis 14:18). Shalem is Yerushalayim, like it says "va'Yhi v'Shalem Suko" (Tehilim 76:3). It is called so, for Yerushalayim is the place of Tzedek (righteousness).
Above (9:2), it says that all the kings of Kena'ani gathered together. Why did only five come to fight the Giv'onim?
Malbim: Hashem thwarted their plans. He made discord among them. The Giv'onim are the Chivi, who gathered with the others to fight Yisrael (9:1). These five kings were irate and came to fight the Giv'onim. They fell to Yehoshua, for they were separated from the gathering of all the kings.
