scabyoudaoicibaDictYouDict[scab 词源字典]
scab: [13] Old English had a word sceabb ‘scab’. This survived into modern English as shab, a dialectal synonym of scab, but it is only represented in the mainstream language by its derivative shabby. It is its Old Norse relative skabbr, borrowed in the 13th century as scab, which has become the general English term for a ‘crust over a wound’.

The derogatory sense ‘strike-breaker’ emerged in the 19th century from an earlier, 16th-century ‘despicable person’. The word comes ultimately from the Germanic base *skab- ‘scratch, shave’ (source also of English shave [OE]), which was descended from the same Indo-European base that produced Latin scabiēs ‘itch’ (source of English scabies [14], scabious [14] – a plant so called because it was supposed to cure skin diseases – and scabrous [17]).
=> scabies, shabby, shave[scab etymology, scab origin, 英语词源]
scab (n.)youdaoicibaDictYouDict
mid-13c., "skin disease," developed from Old English sceabb "scab, itch" (related to scafan "to shave, scrape, scratch") and from Old Norse skabb "scab, itch," both from Proto-Germanic *skab- "scratch, shave," from PIE *(s)kep- "to cut, scrape, hack" (see scabies). Sense reinforced by cognate Latin scabies "scab, itch, mange" (from scabere "to scratch").

Meaning "crust which forms over a wound or sore" is first attested c. 1400. Meaning "strikebreaker" first recorded 1806, from earlier sense of "person who refuses to join a trade union" (1777), probably from meaning "despicable person" (1580s), possibly borrowed in this sense from Middle Dutch.