Wikipedia: In Western Christianity, Lent is the period (or season) from Ash Wednesday to Holy Saturday. In Eastern Christianity, the period before Easter is known as Great Lent to distinguish it from the Winter Lent, or Advent (known in Greek as the "Great Fast" and "Nativity Fast", respectively). This article tends to discuss Lent as understood and practiced in Western Christianity. Easter always falls on a Sunday between March 22 and April 25, roughly corresponding to early spring in the Northern Hemisphere. Ash Wednesday, which may fall anywhere between February 4 and March 10, occurs forty-six days before Easter, but Lent is nevertheless considered to be forty days long, due to the fact that Sundays in this season are not counted among the days of Lent. The traditional reason for this is that fasting was considered inappropriate on Sunday, the day commemorating the Resurrection of Jesus. Easter celebrates the Resurrection of Jesus Christ, while Lent is a time of preparation for Holy Week. Holy Week recalls the events preceding and during the crucifixion, which Christians believe occurred in the Jerusalem of the Roman province Judea, circa AD 30. The forty day period is symbolic of the forty days spent by Jesus in the wilderness; the forty days Moses spent on Mount Sinai with God; the forty days and nights Elijah spent walking to Mt. Horeb; in the story of Noah, God makes it rain for forty days and forty nights (they were in the ark for much longer); the Hebrew people wandered forty years traveling to the Promised Land. Jonah in his prophecy of judgment gave the city of Nineveh forty days grace in which to repent. Jesus is said to have retreated into the wilderness to be tempted by the devil. Jesus fasted for forty days and forty nights. Afterwards He was hungry and the devil tempted Him. Jesus overcame all of the devilish temptation of the lust of the flesh, lust of the eyes and the pride of life by citing Holy Scripture to the devil. The Devil left Him. Holy Angels ministered to Jesus. Now Jesus begins His Galilean ministry. The Lenten period of forty days owes its origin to the Latin word quadragesima, signifying forty hours. This referred to the forty hours of total fast which preceded the Easter celebration in the early Church.[1] The main ceremony was the baptizing of the initiates on Easter Eve. The fast was in preparation to receive this sacrament. Later, the period from Good Friday until Easter Day was extended to six days, to correspond with the six weeks of training, necessary to instruct the converts who were to be baptized. Initially the word simply meant spring, and later became associated with the fast. The English word lent derives from the Germanic root for Spring (specifically Old English lencten; also the Anglo-Saxon name for March - lenct - as the main part of Lent, before Easter, usually occurred in March). A strict schedule was adhered to in the teaching of the converts. In Jerusalem near the close of the fourth century, classes were held throughout seven weeks of Lent for three hours each day. With the imposition of Christianity as the state religion of Rome during this century, its character was endangered by the great influx of new members. To combat this hazard, the Lenten fast and practices of self-renunciation were required of all Christians. The less zealous of the converts were thus brought more securely into the Christian fold.

Thanks to Singwell and anyone else who answers the question.

The forty days' abstinence of Lent was directly borrowed from the worshippers of the Babylonian goddess. Lent of forty days, "in the spring of the year," is still observed by the Yezidis or Pagan Devil-worshippers of Koordistan, who have inherited it from their early masters, the Babylonians. Lent of forty days was held in spring by the Pagan Mexicans, for thus we read in Humboldt, where he gives account of Mexican observances: "Three days after the vernal equinox...began a solemn fast of forty days in honour of the sun." Lent of forty days was observed in Egypt, as may be seen on consulting Wilkinson's Egyptians. This Egyptian Lent of forty days, we are informed by Landseer, in his Sabean Researches, was held expressly in commemoration of Adonis or Osiris, the great mediatorial god. At the same time, the rape of Proserpine seems to have been commemorated, and in a similar manner; for Julius Firmicus informs us that, for "forty nights" the "wailing for Proserpine" continued; and from Arnobius we learn that the fast which the Pagans observed, called "Castus" or the "sacred" fast, was, by the Christians in his time, believed to have been primarily in imitation of the long fast of Ceres, when for many days she determinedly refused to eat on account of her "excess of sorrow," that is, on account of the loss of her daughter Proserpine, when carried away by Pluto, the god of hell. As the stories of Bacchus, or Adonis and Proserpine, though originally distinct, were made to join on and fit in to one another, so that Bacchus was called Liber, and his wife Ariadne, Libera (which was one of the names of Proserpine), it is highly probable that the forty days' fast of Lent was made in later times to have reference to both. Among the Pagans this Lent seems to have been an indispensable preliminary to the great annual festival in commemoration of the death and resurrection of Tammuz, which was celebrated by alternate weeping and rejoicing, and which, in many countries, was considerably later than the Christian festival, being observed in Palestine and Assyria in June, therefore called the "month of Tammuz"; in Egypt, about the middle of May, and in Britain, some time in April. To conciliate the Pagans to nominal Christianity, Rome, pursuing its usual policy, took measures to get the Christian and Pagan festivals amalgamated, and, by a complicated but skilful adjustment of the calendar, it was found no difficult matter, in general, to get Paganism and Christianity--now far sunk in idolatry--in this as in so many other things, to shake hands. The instrument in accomplishing this amalgamation was the abbot Dionysius the Little, to whom also we owe it.