a young street ruffian, especially one belonging to a gang.
1870-75, Americanism; probably < dialectal German; compare Swabian derivatives of Hudel rag, e.g. hudelum disorderly, hudellam weak, slack Hudellump(e) rags, slovenly, careless person, and related words in other dialects
1871, Amer.Eng. (first in ref. to San Francisco) "young street rowdy, loafer," later (1877) "young criminal, gangster," of unknown origin, though newspapers have printed myriad stories concocted to account for it. A guess perhaps better than average is that it is from Ger. dial. (Bavarian) Huddellump "ragamuffin."