Carnival, the merrymaking and festivity that takes place in many Roman Catholic countries in the last days and hours before the Lenten season. The derivation of the word is uncertain, though it possibly can be traced to the medieval Latin carnem levareor carnelevarium, which means to take away or remove meat. This coincides with the fact that Carnival is the final festivity before the commencement of the austere 40 days of , during which Roman Catholics in
earlier times fasted, abstained from eating meat, and followed other ascetic practices. The  historical origin of Carnival is also obscure. It possibly has its roots in a primitive festival honouring the beginning of the new year and the rebirth of nature, though it is also possible that the beginnings of Carnival in Italy may be linked to the pagan Saturnalian festival of ancient Rome

http://www.britannica.com/topic/Carnival-pre-Lent-festival

Protestants don't observe the carnival as they don't regard including the pre-Christian elements into their religious observances as appropriate. However, countries such as Denmark, Austria and Switzerland have their own variations on the Carnival.

As the Europeans established their colonies in Asia and South America, they also influenced these regions with their culture and the Carnival was brought to these regions. As a result, carnivals of South America, Kerala and Goa have their own flavour as they combine the European elements with their local elements and also borrow from other religions in their countries. One such instance is the painting of faces and throwing colours at each other during Goa Carnival, which is obviously an influence of the Hindu colour festival of Holi. In Brazil they like to wear their traditional indigenous tribal head-gear made of gorgeous feathers.

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