Carnival
In Rome the god Saturn was celebrated at the end of the year. During the so-called "Saturnalia" the slaves were served by the free. In honor of the goddess Isis, a ship's chariot was pulled and rocked through the streets. The assumption is that the word carnival derives from this floating chariot ("Carrus navalis"). Later, the pagan cult became a church festival.
The origins of carnival as a church festival go back to the church father Augustine, who allowed believers to free themselves from all the "restrictions of life" for one day in order to then be able to motivate themselves again for church constraints. The forty-day period of Lent followed directly after the excessive celebration of carnival, during which penance and strict abstinence were again expected of the people.
There are no indications in the Bible that believers celebrated Carnival in the early days of Christianity, nor that they observed a ritual fasting period as it is prescribed by the church. In addition, God's Word admonishes us not to let ourselves be ruled by sensual lusts and drives. Participating in celebrations like carnival, however, harbors the real danger of taking pleasure in the sinful doings and thereby making oneself guilty before God.
The Bible advocates fellowship and enjoying life in a godly manner. In contrast, the Bible expressly condemns drunkenness and debauchery, unrestrainedness and self-indulgence as well as sexual fornication, which only serve to satisfy sensual (carnal) desires, as sins. Carnival as such represents a time of sinful debauchery.
In addition, carnival is one of the few opportunities for many people to escape from the gloomy or joyless everyday life and to get "joy" at least for a short time by partying extensively. This in turn reveals the spiritual emptiness that comes with life without God. On the other hand, those who derive their joy of life from constant communion with God are no longer dependent on superficial activities that can at best bring brief satisfaction.
Sources:
Wikipedia
Encyclopedia Britannica
Encyclopedia Americana
Catholic Encyclopedia
Encyclopedia of Religion