Maranatha (either מרנא תא; maranâ' thâ' or מרן אתא; maran 'athâ' ) is an Aramaic phrase occurring once only in the New Testament (see Aramaic of Jesus) and also in the Didache which is part of the Apostolic Fathers collection. It is transliterated into Greek letters rather than translated, and is found at the end of Paul's First Epistle to the Corinthians (1 Cor 16:22) as a farewell. The NRSV translates it as: "Our Lord, come!" but notes that it could also be translated as: "Our Lord has come"; the NIV translates: "Come, O Lord"; the NAB notes:
The phrase may have been used as a greeting between Early Christians, and it is possibly in this way that it was used by the Apostle Paul. However, the preceding word is the curse "anathema", and because the original texts of the Greek New Testament contained no punctuation at all, or indeed any word or sentence separation, early readers took the two words together and construed the passage as, "If any man love not the Lord Jesus Christ, let him be Anathema Maranatha". It was therefore believed that "anathema maranatha" must be some exceptionally severe kind of curse. This indeed is the translation (and implied interpretation) given in the Authorized Version (King James), based on the majority of Greek texts (the Textus Receptus).
The phrase was in use in this sense at least by the 7th Century, when Pope Silverius pronounced anyone who deceives a bishop as "anathema maranatha" (see the Catholic Encyclopedia article referenced below). One possible understanding of this is that the offender would be excluded from communion with the Church until the return of Christ, tying the punishment to the term Maranatha.