EXCOMMUNICATION–JUST AND UNJUST, Ch 9 of The Church and the Priesthood by Ogden

In simple terms, communication includes a connecting, sympathetic relationship, while excommunication involves a disconnection or exclusion. In a Latter-day Saint context, some have thought that excommunication results in some terrible curse or judgment that befalls those cut off from the Church. However, when someone is excommunicated for a gross sin, that person has already incurred a severe judgment, for he has already lost his Priesthood because of his actions, and his excommunication has nothing to do with that loss.

Most churches, notably Christian and Jewish, have a ceremonial program for the punishment of their members. The type of punishment depends on the seriousness of the sin. When greater offenses have been committed, individuals are removed from the general membership of the church. Thus, they are “excommunicated,” “cast out” or “cut off.” Just as a man might have an arm or leg cut off or separated from the body, so is a member separated from the body of the church.

Cutting off. In the Old Testament a penalty or form of punishment used primarily, though not exclusively, for various offenses against the ceremonial laws. The agent of the “cutting off” was either God or the community. (Wycliffe Bible Dictionary, p. 412)