Later that afternoon, Nick and Janet walk home together. They walk one after the other on the edge of the curb, trying to see who can balance without falling. At one point, Janet steps off the curb—she found a fancy gold ballpoint pen. As the two continue along the curb, Nick thinks about his report and what Mrs. Granger said about words.
It's telling that Nick is doing this thinking in Janet's presence. It sets up the precedent that Nick doesn't and cannot act alone; he needs his friends and classmates to help make his ideas realities.
Nick thinks of Mrs. Granger saying that he says that words mean what they do. He remembers that as a toddler, he had a cassette player and sing-along tapes. When he wanted to listen to the tapes, Nick would carry the player and the tapes to someone, bang them together, and say, "gwagala." His family knew what he wanted when he said "gwagala," though he learned in preschool that for others to understand him, he needed to say "music."
Nick's assessment of his unique toddler language highlights the ways in which small groups of people develop their own unique ways of speaking to each other that only they understand. By connecting this to Mrs. Granger's explanation of how the dictionary works, this suggests that Nick recognizes that these unique language systems can become mainstream, but often don't.
Absorbed in his thoughts, Nick bumps into Janet, knocking her off the curb and sending the gold pen flying. Nick apologizes, picks up the pen, and hands it to Janet. As he does, he calls it a frindle. Janet gives Nick a funny look, but Nick runs off and won't explain what a frindle is. By the time he makes it home, Nick has a whole plan worked out.
The next afternoon, Nick walks into a corner store and asks the lady behind the counter for a frindle. It takes a minute and Nick has to point to the pens, but the lady finally sells Nick a pen. Every day for the next six days, one of Nick's friends goes in after school and asks the lady for a frindle. By the time Janet asks for a frindle on the sixth day, the lady knows exactly what she's talking about. Nick thinks that "frindle" is now a real word. A bit later, Nick and five of his friends meet in his play room and sign an oath to only use the word "frindle" and never again use the word "pen."
This small experiment with the word illustrates how new words can enter the mainstream and become accepted. It takes constant use and repetition, and Nick has to draw in people he doesn't know and get them to use the word. This shows that while Nick is the leader of this crusade, there's only so much he can do alone. The success of "frindle" rests on people like this saleslady understanding what it means and using it.