sourdough

From Middle English sour dogh, simply sour + dough. Germanic languages have close cousins of the word — Dutch zuurdeeg, German Sauerteig, Danish surdej, Swedish surdeg, Icelandic súrdeig — all naming the same fermented starter.

In California and later during the Klondike and Alaska gold rushes, prospectors carried pouches of bread starter on their belts or around their necks to keep it alive on the trail. Experienced miners became known by the very starter they carried, and the word came to mean the person as much as the paste.

It shares its roots directly with Dutch zuurdeeg and German Sauerteig, all literally 'sour dough' in their own tongues.