The story
1915, alteration of dialectal scrunge ("to search stealthily, rummage, pilfer") (1909), of uncertain origin, perhaps from dialectal scringe ("to pry about"); or perhaps related to scrouge, scrooge ("push, jostle") (1755, also Cockney slang for "a crowd"), probably suggestive of screw, squeeze. Popularized by the military in World War I.
Etymology from Wiktionary, CC BY-SA 4.0.