The Creed of Constantinople

Why is the Creed of Constantinople (AD 381) called the Nicene Creed? The liturgy of the Book of Common Prayer actually provides what I think is the best description of the Great Creed utilised in the Eucharist, as the BCP calls it the 'Creed commonly called Nicene.' The exact origin of the Creed we today use as the Great Creed in Eucharistic worship, for the whole Catholic Church both East and West, has been lost in the mists of time. The answer to the question is not itself simple but can be reduced to a simplistic phrase: the Constantinopolitan Creed is identified with the Nicene Creed because the Council that officially ratified it, the Fourth Ecumenical Council of Chalcedon (AD 451), did so. Chalcedon confused the Creed of Nicea with the Creed of Constantinople because the Council of Constantinople professed that its teaching was the true expression of Nicene faith and orthodoxy. The reason for all this is shrouded in mystery; all we know for certain is that the First Council of Constantinople in AD 381 led in time, likely after the period of the Council itself, to the creation of a new Creed, an expansion of a third-century baptismal creed used in the Church of Jerusalem, which was called the 'Faith of the 318 Fathers,' that is, the Faith of the First Ecumenical Council of Nicea I. It is possible that Saint Cyril of Jerusalem presented the form of the Constantinopolitan Creed to the Council of AD 381 from his own Church: this however is an ancient tradition and not based on certain evidence. This much we do know - in turn, the 'Creed of the 150 Fathers,' that is, the Creed of Constantinople I, was declared to be same as the Creed of Nicea I by the Council of Chalcedon in 451. Chalcedon also stated that the Creed of Constantinople (C), which was confused with the original Creed of Nicea (N), was to be unchanged and unaltered forever - and that any effort to change, alter, or correct the Creed so received would be heresy. The whole subject is fascinating and definitely worth careful study. What I find most compelling about the historical quandary raised herein is that, in the end, it is really unimportant; it forces us to depend on the undeniable authority of Holy Tradition and the mind of the One, Holy, Catholic, and Apostolic Church for the faith and use of the Creeds. We use the Creeds based, not on the authority of their origin or construction, but on their reception and use by the whole Undivided Church. How Anglican! The Creeds squeeze us out of subjective and protestant private judgement and steer us into the bosom of the Church for our guiding authority. I highly recommend a classic work on the subject, Early Christian Creeds by JND Kelly, for further information.