Chester Copperpot is an adventurer from the movie The Goonies.
He died trying to get One Eyed Willy's treasure, (many years before the timeframe of the movie).
The kids first hear about him in a newspaper clipping. They later discover his dead body squashed under a large rock after they are fairly far into "One Eyed Willy"'s maze of traps.
Chunk: Hey, you guys, look at this. Hey, you guys ever heard of this guy? Look, Chester Copperpot?
Data: (Reading) Chester Copperpot?
Chunk: Okay it says, "Chester Copperpot: Missing while in pursuit of local legend. Reclusive scavenger claims, 'I have the key to One-eyed Willy'."
Mikey: Whoa, do you guys realize what we could do?
Brand: Nobody ever found nothing, you guys. I mean, why do you think this map would be up here in this attic when it could be in some safety deposit box somewhere, right?
Mouth: That's right. And anyway, if Chester Copperpot didn't find it, how would we find it?
Mikey: (Whispering to himself) Chester Copperpot...Chester Copperpot... (Out loud, to the rest) Chester Copperpot! Don't you guys see? Don't you realize? He was a pro. He never made it this far. Look how far we've come. We've got a chance.