Last week, readers @amyh914 and @johnjaramillo13 were wondering about the origins of “scab” as an insult for people who cross picket lines. John believes it “[infers] disease and ugliness,” and he’s got it right—but let’s fill in the details.

According to the Oxford English Dictionary, “scab” was first recorded in English around 1250, and referred to diseases of the skin. Two hundred years later, it appeared with the common definition we know today, a hard crust that forms over a wound.

By the 1500s, it had taken on a secondary meaning in England. As a slang insult for a “mean, low, ‘scurvy’ fellow; a rascal, scoundrel,” it drew a connection between that person and scabs -- and the diseases and sores that lead to them (syphilis, for example) -- and, by extension, bad habits and unclean lifestyles.

By the late 1700s, laborers adopted the insult to refer to workmen who wouldn't join a strike, a union, or take part in organized labor. One of the earliest known recordings is from 1777: “the Conflict would not been [sic] so sharp had not there been so many dirty Scabs; no Doubt but timely Notice will be taken of them." Early in the next century, "scab" became even more specialized and started being applied specifically to workers who crossed picket lines to take the place of striking workers, as in this testimony from the trial of striking Philadelphia bootmakers: “I concluded at that time I would turn a scab, unknown to them, and I would continue my work and not let them know of it.”

In Household Words, Stephanie Smith draws a clear line from the one definition to the other:

From blemish … to strikebreaker, the history of the word scab … shows a displacement of meaning from the visceral or physical to the moral register … Just as a scab is a physical lesion, the strikebreaking scab disfigures the social body of labor—both the solidarity of workers and the dignity of work.

Smith also points out that the term has mellowed some since it first entered the labor vocabulary. “Scab” used to be thrown into conversation like a bomb. It was so vile and politically and emotionally charged that it caused shame and anger. Its power seems to have diminished a bit since the days when a piece of union literature, generally attributed to author Jack London, said:

"After God finished the rattlesnake, the toad, the vampire, He had some awful substance left with which He made a scab … When a scab comes down the street, men turn their backs and angels weep in heaven, and the Devil shuts the gates of Hell to keep him out. No man has a right to scab so long as there is a pool of water to drown his carcass in, or a rope long enough to hang his body with."

They don't make insults quite like that anymore.