shabbyyoudaoicibaDictYouDict[shabby 词源字典]
shabby: [17] Etymologically, shabby means ‘scabby’. It comes from a now obsolete shab, which denoted ‘scab’, and also metaphorically ‘disreputable fellow’. It was the native equivalent to Old Norse *skabbr ‘scab’, from which English gets scab.
=> scab[shabby etymology, shabby origin, 英语词源]
shabby (adj.)youdaoicibaDictYouDict
1660s, of persons, "poorly dressed," with -y (2) + shab "a low fellow" (1630s), literally "scab" (now only dialectal in the literal sense, in reference to a disease of sheep), from Old English sceabb (the native form of the Scandinavian word that yielded Modern English scab; also see sh-). Similar formation in Middle Dutch schabbich, German schäbig "shabby."

Of clothes, furniture, etc., "of mean appearance, no longer new or fresh" from 1680s; meaning "inferior in quality" is from 1805. Figurative sense "contemptibly mean" is from 1670s. Related: Shabbily; shabbiness. Shabby-genteel "run-down but trying to keep up appearances, retaining in present shabbiness traces of former gentility," first recorded 1754. Related: Shabaroon "disreputable person," c. 1700.