Excommunication also exists in
Judaism- it's known as
cherem, a word which literally meant "destruction". In
Europe in the
Middle Ages, excummunication could be instituted by any
Beis Din, or local
tribunal of
rabbis, and it was a popular weapon against
deviancy. The tribunal would send letters to other Jewish communities informing them of the ban, which forbade exchanging words or doing
business with the excommunicated person, who would be unable to even buy
food from other Jews. So cut off from Jewish contact, this person would be forced to
convert to
Christianity or he/she would die.
One typical cherem was the one pronounced on
Baruch Spinoza. See
The Anathematization of Baruch Spinoza.