It is well known that the word behind Christ-'mas' (shortened form of 'Christ's Mass) is 'mæsse', which comes from the Latin 'missa', the same word used for the Roman Catholic 'Mass' / Holy Eucharist.
Are there historical accounts which show that the Christian use of the term 'missa' is (hopefully) coincidental and that we are not accidentally celebrating a feast that initiated with, and is closely connected to the Roman Catholic mass, which is obligatory on both Dec24 & 25th?
The History of Christmas has this to say:
The earliest evidence of Christ's birth being marked on December 25 is a sentence in the Chronograph of 354. Liturgical historians generally agree that this part of the text was written in Rome in AD 336. Though Christmas did not appear on the lists of festivals given by the early Christian writers Irenaeus and Tertullian, the early Church Fathers John Chrysostom, Augustine of Hippo, and Jerome attested to December 25 as the date of Christmas toward the end of the fourth century. December 25 was the traditional date of the winter solstice in the Roman Empire, where most Christians lived, and the Roman festival Dies Natalis Solis Invicti (birthday of Sol Invictus, the 'Invincible Sun') had been held on this date since 274 AD.
The article goes on to explain that the prominence of Christmas Day gradually increased after Charlemagne was crowned Emperor on Christmas Day in 800. King Edmund the Martyr was anointed on Christmas in 855 and King William I of England was crowned on Christmas Day 1066.
During the 17th century the English Puritans condemned the celebration of Christmas, considering it a Catholic invention and the “trappings of popery” or the “rags of the beast”. Calvinist clergymen and the Presbyterian Church of Scotland disapproved of Christmas celebrations. Even though King James VI of Scotland (who later became King James I of England, Ireland and Wales) commanded its celebration in 1618, attendance at church was scant. Those pesky Protestants!
With regard to the choice of dates it seems that it is no coincidence or accident that Christians are celebrating what originated as a Catholic Mass.
The 'history of religions' theory suggests the Church chose December 25 as Christ's birthday (dies Natalis Christi) to appropriate the Roman winter solstice festival dies Natalis Solis Invicti (birthday of Sol Invictus, the 'Invincible Sun'), held on this date since 274 AD. Some early Christian writers noted the solar symbolism in placing Jesus's birthday at the winter solstice and John's birthday at the summer solstice. Another theory, the 'computation hypothesis' or 'calculation theory', notes that December 25 is nine months after March 25, a date chosen as Jesus's conception (the Annunciation) and the date of the spring equinox on the Roman calendar.
Protestants distance themselves from the historical and religious history and would deny that they have anything to do with any Catholic Mass. Quakers and Jehovah’s Witnesses do not celebrate Christmas because of its pagan and Catholic origins.
Christ-'MAS' = 'Mæsse' = Latin 'Missa' = Catholic 'Mass' / Holy Eucharist
The Feast of the Nativity of Our Lord Jesus Christ is cultural expressed as a Christmas Mass. The term Christmas is employed these days that celebrates the Birth of Christ without any thought to a literal connection to a Catholic Mass celebrated on this day.
According to Catholicism, the Feast celebrated on this day of Christmas is the Feast of Nativity of Our Lord Jesus Christ in the flesh. The term Christmas is a cultural way of expressing this.
Christmas is an annual festival commemorating the birth of Jesus Christ, observed primarily on December 25 as a religious and cultural celebration among billions of people around the world. A feast central to the liturgical year in Christianity, it follows the season of Advent (which begins four Sundays before) or the Nativity Fast, and initiates the season of Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night. Christmas Day is a public holiday in many countries, is celebrated religiously by a majority of Christians, as well as culturally by many non-Christians, and forms an integral part of the holiday season surrounding it.
Etymology
The English word Christmas is a shortened form of 'Christ's Mass'. The word is recorded as Crīstesmæsse in 1038 and Cristes-messe in 1131. Crīst (genitive Crīstes) is from the Greek Khrīstos (Χριστός), a translation of the Hebrew Māšîaḥ (מָשִׁיחַ), 'Messiah', meaning 'anointed'; and mæsse is from the Latin missa, the celebration of the Eucharist.
The form Christenmas was also used during some periods, but is now considered archaic and dialectal. The term derives from Middle English Cristenmasse, meaning 'Christian mass'. Xmas is an abbreviation of Christmas found particularly in print, based on the initial letter chi (Χ) in the Greek Khrīstos ('Christ'), although some style guides discourage its use. This abbreviation has precedent in Middle English Χρ̄es masse (where Χρ̄ is an abbreviation for the Greek Χριστός). - Christmas
I hate to answer my own question, but it is certainly worth to share the research I have done after posting this question, and to stimulate further discussion: