c.1250, "skin disease," developed from O.E.
sceabb "scab, itch" (related to
scafan "to scratch") and from O.N.
skabb "scab, itch," both from P.Gmc.
*skab- "scratch, shave" (related to
shabby). Sense reinforced by cognate L.
scabies "scab, itch, mange" (from
scabere "to scratch;" see
scabies). 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" (1590), possibly borrowed in this sense from M.Du.