Who is Jumbo from Neither Wolf nor Dog: On Forgotten Roads with an Indian Elder and what is their importance?

Jumbo is the name of the four hundred pound garage mechanic who fixed Nerburn's Nissan truck. His shop was in a run-down concrete building with a garage door sign that said, "Broke Car's and Stuff'fixed. 'Not running 'ok' Jumbo". Nerburn's truck had stopped and would not run anymore. Jumbo came out wearing a dirty white T-shirt hanging over his belly that hung over his belt buckle. He looked at Nerburn's truck, and when Nerburn asked if he could fix it, asked him what it was. Most of the vehicles he saw around were Fords, Chevys and beat-up pickup trucks. The garage door opened up and Jumbo had the truck pushed over the grease pit. He said he could fix it. Nerburn asked how long, but Jumbo said he didn't know. When Nerburn returned from the trip with Dan and Grover, the truck was done and Jumbo charged him twenty bucks.