I recently started Kendo and had a sore left pinkie after my first practice. The proper grip of a Japanese sword relies on a grip focused on the pinkie of the left hand. Today, I learned that the tradition of chopping the left pinkie as punishment for disgrace was based on this fact. Without a left pinkie, it's quite difficult to grip a Japanese sword.
In the May 15 incident the Prime Minister of Japan, Tsuyoshi Inukai was assassinated by eleven young Naval Officers. After the court martial, eleven severed fingers were sent to the court house.
Today, the Yakuza continue this tradition, even though swords are no longer the weapon of choice.