Where does death before dishonor originate?

It was derived from a Roman phrase. The Latin saying was: "Mors Ante Infamiam" "infamiam" meaning "infamy". ("dishonour" is a synonym.)

Another version of the phrase was: "Potius Mori Quam Foedare," which means "rather to die than to be dishonoured". This was the motto of the Duchy of Brittany. (In Breton it is "Kentoc'h mervel eget bezañ saotret").

Breton soldiers and mariners may have brought the motto to England and France in the Middle Ages.

The national emblem of Brittany, the ermine, has the same meaning. As the Bretons married into the royal houses of Europe, the use of the ermine spread.