A JKR respondeu isso em uma das entrevistas. AFAIR, o processo em sua mente foi, surpreendentemente, diferente do hacking na vida real (você investiga e muda o ataque baseado no feedback do sistema para suas tentativas de tentativa e erro).
De " MuggleNet e The Leaky Cauldron entrevista Joanne Kathleen Rowling "
16 de julho de 2005: Harry Potter e o Príncipe Misterioso publicam dia em Edimburgo, Escócia - Parte Três.
MA: How did they figure out how to work the map?
JKR: Don't you - well. This is how I explained it to myself at the time, and this does sound glib. Don't you think it would be quite a Fred and Georgeish thing to say in jest, and then see this thing transform?
MA: Yeah.
JKR: Can't you just see them?
ES: But the exact word combination? Is that just a lot of luck, or Felix Felicis -
JKR: Or, the map helped.
MA: Yep, yeah. You can see them sort of answering and joking with each other -
JKR: And the map flickering into life here and there when they got closer and closer, and finally they hit upon the exact right word combination and it just erupts.