The Sword Emperor is a title addressed to one person who excels in swordplay above all others. Even after winning the title, whomever currently holds it must still fight 100 battles to secure it.
Before Squalo was the Sword Emperor, Tyr was the Sword Emperor. It was also revealed that Tyr was the Varia's leader before Xanxus. Because he had no left hand, Squalo cut off his own to understand what it was like to use and fight like the Sword Emperor. Later, Squalo sends Yamamoto 100 videos on how he secured his title as the second Sword Emperor by defeating 100 people in a row. He also had an extra video (thus having 101 battles) because he didn't count the battle with Genkishi, as he realized that Genkishi wasn't actually putting effort into the battle.