You come from another universe where everyone speaks a different language and chooses their own names.
One day, you were walking in a glade surrounded by purple sparkly trees, when you happened to come across a floating orb of blue light. The orb uttered a strange voice, then your body exploded.
At the same time you died, you were reborn in someone else's body and decided to call yourself pangtongshu, because in your language, pang means 'death of', tong means 'blue', and shu means 'light'.