What is the history of Fasching?

We know from an account by the medieval German poet Wolfram von Eschenbach that Fasching was celebrated in Germany as early as the 13th Century. However, its roots most certainly go back much further. Fasching incorporates many pre-Christian pagan beliefs with Catholic tradition and was likely celebrated as a festival to celebrate the coming of spring going back many centuries.
Germanic pagan traditions likely combined with those of Rome to create this celebration in its earlier forms. Before Christianity, it was seen as a way to drive away the winter spirits and welcome those of spring. As such, it is a celebration of the coming fertility of the season.
Furthermore, Fasching is a celebration of role reversals, with the daily norms being turned upside down. Women were given symbolic roles of power, madmen and lunatics were given seats on the town board, servants gave orders to their masters, and noisy parades of ribald drinkers took to the streets. This is likely an adaptation of the Roman festival of Saturnalia.
The festival was also associated with a feast for all people of the community. This was a big deal, since the end of winter was usually a time of hunger for the poor. On this day, winter stores of lard, butter, and salted meat were emptied out to serve as a public feast alongside selected livestock which were held in reserve for just this occasion. Fasching was a time for indulgence of the practices that would soon be given up for Lent.
While Fasching remains celebrated by many German Catholics, it was largely abandoned in many areas during the Protestant Reformation. The reformers of the 16th century saw Fasching as a symbol of the excessiveness of the Catholic Church and therefore distanced themselves from the celebration.
https://www.german-way.com/history-and-culture/holidays-and-celebrations/fasching-and-karneval/