Some of the most unbelievable parts of the show (based on the book by Dan Simmons) are true. The adventures still capture the imagination of Britons to this day. The expedition did happen. It was Franklin's third and final expedition to the Northwest Passage, the Arctic route that links the Atlantic and the Pacific.

The Reign of Terror (French: la Terreur) was a period of the French Revolution when, following the creation of the First Republic, a series of massacres and numerous public executions took place in response to revolutionary fervour, anticlerical sentiment, and accusations of treason by the Committee of Public Safety.

The slang bet appears to come from the everyday word bet, a wager  or to risk something of value.  By the 1850s, we were saying You bet! as an affirmative exclamation with the sense of Indeed!  This expression has the underlying notion of You can bet that it is so or That's a bet.

Dog  Short for underdog. Even  What you see next to a game when no team is given better odds. Short for even money. Sometimes called a pick 'em game. If you bet $10 and your team or player wins, you win $10.