Jake Epping (first appeared in 11/22/63)

Jake Epping is mentioned in the following books:

The Tommyknockers (Nov 1987)

A bit of a stretch (maybe - it doesn't seem like Stephen King does anything by accident), but there's a minor character called Henry Amberson in The Tommyknockers who is one of the casualties of the changes in Haven, when his pacemaker explodes. He might be a reference to Jake's alias in 11/22/63, George Amberson. Perhaps the real George Amberson grew up in Haven with Henry?

“A forest ranger from Newport died,” Dawson said reluctantly. “Who?” “Henry Amberson.” “What? Henry? Christ!” Torgeson felt as if he had been hit hard in the pit of the stomach. He had known Henry Amberson for twenty years—the two of them hadn’t been best friends, nothing like it, but they had played some cribbage together when times were slow, done a little fly-fishing. Their families had taken dinner together. Henry, Jesus, Henry Amberson. And Tierney was in fucking Utah. “Was he in one of the Jeeps they sent out?” “Yeah. He had a pacemaker, you know, and—” “What? What?” Torgeson took a step toward Smokey as if to shake him. “What?” “The guy driving the Jeep apparently radioed in to Three that it exploded in Amberson’s chest.”
- Book III / Chapter 9 / Section 2