Sourdough is slang for an experienced hunter or prospector in the Alaskan and Canadian bush. That's because experienced woodsmen treasured and used their sourdough bread starter. Many kept it in a pouch around their neck. The term is at least as old as the Klondike gold rush.

Technically you couldn’t be considered a sourdough until you'd survived the north for at least a year. But once upon a time a cheechako (tenderfoot) came into an Alaskan bar and asked "What does a fellow have to do to be considered a sourdough?"

The barkeep was willing to be amused. "Well, sir, there are three things. You have to drink a quart of rye whisky in one go. You have to make love to an Esquimaux woman. And you have to track down a Kodiak bear."

"Hey, I can do that!" says our hero. "Give me that bottle!" Soon he staggered out of the bar and Boniface forgot about the matter. A week later the cheechako dragged himself back. He was torn, bruised, bloody, and a generally horrible sight. "Whisky!" he croaked. After several drinks he asked the barkeep "Okay, tell me about this Esquimaux woman I'm supposed to track down."