During the dark days of the mogu dynasties, pandaren slaves were not permitted weapons of any kind. When training in secret, pandaren monks would often use farm tools or simple bamboo staves for practice. Emphasis was also placed on unarmed strikes.
In contrast, the favored weapons of the mogu were based on fear rather than practicality. They were large, cumbersome, and difficult to wield. Pandaren monks took advantage, developing fast strikes and the skill to quickly move around the battlefield. The larger, slower mogu were often completely disoriented by the speed of the pandaren monks in open combat.
Over the years, fighting styles have changed dramatically, incorporating any number of other abilities, weapons, styles, etc. But the core foundation of pandaren fighting techniques remains the same: Defeat an opponent of any size with your bare paws if you have to.