Pippi was actually named by Astrid Lindgren's daughter, Karen. Apparently, when Karen was home sick from school one day, she asked her mom to tell her a get-well story, and Pippi was born.
In the original Swedish, she's Pippi Langstrump. In German, Pippi Langstrumpf. But why stop there? In Italian, she's Pippi Calzelunghe, and in Turkish, Pippi Uzunçorap. In Thai: Pippi Thung-Taow Yao. In Welsh: Pippi Hosan-hi. In Ukrainian: Peppi Dovhapanchokha. In French: Fifi Brindacier. In Icelandic: Lína Langsokku. In Armenian: Erkaragulpa Pipin. And of course, in English: Pippi Longstocking.
What's our point? We have two, actually. First, that this book has been translated into more than seventy languages. And second, that no matter where you go, the book is titled for its title character—a character so unique (and strong, and charismatic, and forceful) that no other title would do.