Eta were the social outcast in feudal Japan. They were shunned by the other classes because their death-related occupations such as butchering and leather tanning. These occupations rendered them spiritually unclean in the view of the Shinto believe.
They lived apart from the rest of the population in slums on the outskirts of town. They couldn’t marry outside their class, or otherwise escape from it. They performed the dirtiest and most menial of tasks: emptying cesspools, collecting garbage, clearing away bodies after floods, tires, and earthquakes - and staffing the jail and morgue.
Their standing was so low a samurai could kill them on a whim - to test a new sword, if he so desired - without fear of reprisal.