"eruption of small red spots on skin," 1709, perhaps from French rache "a sore" (Old French rasche "rash, scurf"), from Vulgar Latin *rasicare "to scrape" (also source of Old Provençal rascar, Spanish rascar "to scrape, scratch," Italian raschina "itch"), a variant of classical Latin rasitare, from Latin rasus "scraped," past participle of radere "to scrape" (see raze (v.)). The connecting notion would be of itching. The figurative sense of "any sudden outbreak or proliferation" is recorded by 1820.

"A rascally, disorderly, or despicable person" [Century Dictionary], 1690s, alteration of rascallion (1640s), a fanciful elaboration of rascal (q.v.). It had a parallel in now-extinct rampallion (1590s), from Middle English ramp (n.2) "ill-behaved woman." Also compare rascabilian (1620s). Rapscallionry "rascals collectively" is marked "[Rare.]" in Century Dictionary (1897); Galsworthy used rapscallionism.

1570s, "low and vulgar people collectively;" 1590s, "character or actions of a rascal;" see rascal + -ity. Middle English had rascaldry "common soldiers" (mid-15c.); Carlyle (1837) used rascaldom "the sphere or domain of rascals."

"low, mean, unprincipled, characteristic of a rascal," 1590s, from rascal + -ly (1). The earlier adjective was simply rascal (early 15c.).

*rēd-, Proto-Indo-European root meaning "to scrape, scratch, gnaw."

It forms (possibly) all or part of: abrade; abrasion; corrode; corrosion; erase; erode; erosion; radula; rascal; rase; rash (n.) "eruption of small red spots on skin;" raster; rat; raze; razor; rodent; rostrum; tabula rasa.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit radati "scrapes, gnaws," radanah "tooth;" Latin rodere "to gnaw, eat away," radere "to scrape;" Welsh rhathu "scrape, polish."