The term “scab” is a strikebreaker, it refers usually to an employee that formerly was not hired by the company entangled in the contemporary trade dispute or an employee (union or non union) that disrespects picket lines and attends work during an ongoing strike.
A quote commonly attributed to Jack London begins:
After God had finished the rattlesnake, the toad, and the vampire, he had some awful substance left with which he made a scab. A scab is a two-legged animal with a corkscrew soul, a water brain, a combination backbone of jelly and glue. Where others have hearts, he carries a tumor of rotten principles. 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….”