Laurie and Xor set out from Permute with their new map. They finally knew where they were, where they were going, and how to get there. It was all right there on paper.

“The places on this map have funny names,” said Laurie. “Truncate. What’s that?”

“To Truncate is to make something shorter by cutting off part of it. The town of Truncate has very precise borders,” Xor said.

“Oh. So what’s Axiom?” Laurie asked.

“An Axiom is a rule that you pretend is true even if you don’t know why it’s true,” said Xor.

“Really?”

“Surely. My cousin Nand taught me all about it. She’s a Euclidosaurus.”

“You’re making stuff up again, Xor.”

“No, it’s just one of those things,” the lizard shrugged, turning gray-green. “Either you believe in Axioms or you don’t.”

“Oh yeah? I bet you don’t know what a Furfnoodle is,” Laurie said.

“It’s a . . . I mean, um. I give up. What is it?”

“A Furfnoodle is a kind of bird,” she said. “With long, blue feathers! And it loves eating little lizards.”

“Really?” Xor looked worried and checked the sky for blue feathers.

“No. But if I ever see a big, blue bird that loves to eat lizards, I’m going to call it a Furfnoodle.”

“You really shouldn’t make up words like that,” said Xor.

“If you can make up words, so can I,” Laurie said.

“I was telling the truth, Laurie.”

“It’s even fun to say!” she said. “Furfnoodle.”

“But—”

“Furfnooooodle!” she sang.

“Look, it’s not safe—”

“Furfnoodle. Furfnoodlefurfnoodle. Furf. Nood. Ull!”

There was a bloop sound, and a tiny mouse-looking creature appeared on the path in front of them.

“Furfnoodle!” it said in a tiny mouse voice. It ran around them a few times, then zipped off into the weeds, still screaming. “Furfnoodle! Furfnoodle!”

“What on Earth was that?!” Laurie said.

“That,” said Xor, “was a baby Jargon.”

“Where did it come from? It just blooped out of the air.”

“You made it with . . . that word.”

“I made it?”

“I tried to warn you,” Xor said. “Where did you think Jargon came from?”

“What’s so special about Furf—that word?”

“It’s a name that only means something to you. That’s what a Jargon is,” Xor said. “You made it. It’s yours.”

“But why?”

“No one knows,” he said. “It’s one of those Axiom things. You have to be careful with names. They have a power all their own.”