Before 1970, a retiring bishop would not be given the title of bishop emeritus, but rather be assigned to a titular see, and thus be known as the Titular Bishop of X instead of Bishop emeritus of X. In some cases, a retiring bishop was even promoted to become a titular archbishop of some diocese that no longer existed. For example, Bishop Pieter Nierman, first bishop of the re-established Diocese of Groningen, became the Titular Bishop of Oppidum Consilinum upon his retirement in 1969.
In 1970, Blessed Pope Paul VI decided, that a retiring bishop “continue to be identified by the name of the see they have resigned.” Thus the bishop emeritus came into being. Today, not only retired bishops are emeriti, but diocesan bishops who have been transferred to some office in the Roman Curia are also emeriti. For example, the former bishop of Limburg in Germany, Franz-Peter Tebartz-van Elst is now a delegate for catechesis in the Pontifical Council for the Promotion of the New Evangelisation, but is simply known as Bishop emeritus of Limburg.
Did Pope Francis today return to the old practice? Archbishop Alfredo Zecca of Tucumán in Argentina retired for health reasons at the age of 68 (seven years before the mandatory retirement age). Today’s daily bulletin duly mentions this, but adds that the Holy Father “at the same time transfer(s) him to the titular see of Bolsena”. Archbishop Zecca is then, at least in title, no longer attached to Tucumán, which he headed as archbishop since 2011. Is this indeed a return to the past, or an indication that Archbishop Zecca can expect another assignment when and if his health permits? Whatever the case may be, the appointment does stand out as unusual.