Septuagesima and Lent are both times of penance, Septuagesima being a time of voluntary fasting in preparation for the obligatory Great Fast of Lent. The theme is the Babylonian exile, the "mortal coil" we must endure as we await the Heavenly Jerusalem. Sobriety and somberness reign liturgically; the Alleluia and Gloria are banished
The Sundays of Septugesima are named for their distance away from Easter:
* The first Sunday of Septuagesima gives its name to the entire season as it is known as "Septuagesima." "Septuagesima" means "seventy," and Septuagesima Sunday comes roughly seventy days before Easter. This seventy represents the seventy years of the Babylonian Captivity. It is on this Sunday that the alleluia is "put away," not to be said again until the Vigil of Easter.
* The second Sunday of Septuagesima is known as "Sexagesima, which means "sixty". Sexagesima Sunday comes roughly sixty days before Easter.
* The third Sunday of Septuagesima is known as "Quinquagesima," which means "fifty" and which comes roughly fifty days before Easter.
Quadragesima means "forty," and this is the name of the first Sunday of Lent and the Latin name for the entire season of Lent.
Throughout this short Season and that of Lent (next Season) you will notice a deepening sense of penance and somberness, culminating in Passiontide (the last two weeks of Lent), that will suddenly and joyously end at the Vigil of Easter on Holy Saturday when the alleluia returns and Christ's Body is restored and glorified.
(Latin septuagesima, the seventieth).
Septuagesima is the ninth Sunday before Easter, the third before Lent known among the Greeks as "Sunday of the Prodigal" from the Gospel, Luke 15, which they read on this day, called also Dominica Circumdederunt by the Latins, from the first word of the Introit of the Mass. In liturgical literature the name "Septuagesima" occurs for the first time in the Gelasian Sacramentary. Why the day (or the week, or the period) has the name Septuagesima, and the next Sunday Sexagesima, etc., is a matter of dispute among writers. It is certainly not the seventieth day before Easter, still less is the next Sunday the sixtieth, fiftieth, etc. Amularius, "De eccl. Off.", I, I, would make the Septuagesima mystically represent the Babylonian Captivity of seventy years, would have it begin with this Sunday on which the Sacramentaries and Antiphonaries give the Introit "Circumdederunt me undique" and end with the Saturday after Easter, when the Church sings "Eduxit Dominus populum suum." Perhaps the word is only one of a numerical series: Quadragesima, Quinquagesima, etc. Again, it may simply denote the earliest day on which some Christians began the forty days of Lent, excluding Thursday, Saturday, and Sunday from the observance of the fast.
Septuagesima is today inaugurated in the Roman Martyrology by the words: "Septuagesima Sunday, on which the canticle of the Lord, Alleluja, ceases to be said". On the Saturday preceding, the Roman Breviary notes that after the "Benedicamus" of Vespers two Alleluias are to be added, that thenceforth it is to be omitted till Easter, and in its place "Laus tibi Domine" is to be said at the beginning of the Office. Formerly the farewell to the Alleluia was quite solemn. In an Antiphonary of the Church of St. Cornelius at Compiègne we find two special antiphons. Spain had a short Office consisting of a hymn, chapter, antiphon, and sequence. Missals in Germany up to the fifteenth century had a beautiful sequence. In French churches they sang the hymn "Alleluia, dulce carmen" (Guéranger, IV, 14) which was well-known among the Anglo-Saxons (Rock, IV, 69). The "Te Deum" is not recited at Matins, except on feasts. The lessons of the first Nocturn are taken from Genesis, relating the fall and subsequent misery of man and thus giving a fit preparation for the Lenten season. In the Mass of Sunday and ferias the Gloria in Excelsis is entirely omitted. In all Masses a Tract is added to the Gradual.
SOURCE: The Catholic Encyclopedia (www.newadvent.org)
Why is this Sunday called "Septuagesima"?
Because in accordance with the words of the First Council of Orleans, some pious Christian congregations in the earliest ages of the Church, especially the clergy, began to fast seventy days before Easter, on this Sunday, which was therefore called Septuagesima" - the seventieth day. The same is the case with the Sundays following, which are called Sexagesima, Quinquagesima , Quadragesima, because some Christians commenced to fast sixty days, others fifty, others forty days before Easter, until finally, to make it properly uniform, Popes Gregory and Gelasius arranged that all Christians should fast forty days before Easter, commencing with Ash-Wednesday.
Why, from this day until Easter, does the Church omit in her service all joyful canticles, alleluia’s, and the Gloria in excelsis etc?
Gradually to prepare the minds of the faithful for the serious time of penance and sorrow; to remind the sinner of the grievousness of his errors, and to exhort him to penance. So the priest appears at the altar in violet, the color of penance, and the front of the altar is covered with a violet curtain. To arouse our sorrow for our sins, and show the need of repentance, the Church in the name of all mankind at the Introit cries with David: The groans of death surrounded me, the sorrows of hell encompassed me: and in my affliction I called upon the Lord, and he heard my voice from his holy temple. (Ps. XVII, 5-7.) I will love thee, O Lord, my strength; the Lord is my firmament, and my refuge, and my deliverer. (Fs. XVII. 2-3.) Glory be to the Father, etc.
PRAYER: O Lord, in your kindness hear the prayers of your people. We are being justly punished for our sins, but be merciful and free us for the glory of your name. Through Jesus Christ your Son, our Lord, who lives and reigns with you in the unity of the Holy Spirit, one God, for ever and ever. Amen. (Maryknoll Missal)
FROM: Goffine’s Devout Instructions