Here are the "collects" (opening prayers) for the third and fourth Sundays in Advent, from the 1549 Book of Common Prayer (in modern English):
Lord, we beseech You, give ear to our prayers, and by Your gracious visitation lighten the darkness of our heart, by our Lord Jesus Christ.
Lord, we pray that You will raise up Your power, and come among us, and with great might succour us; that whereas through our sins and wickedness we are sorely obstructed and hindered, Your bountiful grace and mercy through the satisfaction of Your Son our Lord may speedily deliver us; to Whom with You and the Holy Spirit be honour and glory, world without end.
"Succour" is not a very commonly used word these days. According to Oxford, it means "assistance and support in times of hardship and distress." In its verb form, it means to "give assistance or aid to" someone, with this example: "prisoners of war were liberated and succoured." So the word carries the sense of aid and rescue in the midst of great distress.
"Satisfaction" connotes the sacrificial atonement of Jesus Christ upon the Cross for our sins, bearing God's wrath for our sins in our stead, satisfying God's justice and holiness, and being raised on the third day as the sign of the Father's satisfaction with the Son's sacrifice.
Overall, the second prayer carries the sense that from out of the midst of great darkness, set about on every side by our own sinfulness, we cry out to God to come and rescue and deliver us by His grace and mercy: a cry that goes back well over two millennia, long before the time of Jesus, to the days of David's Psalms and the writings of the Prophets, who looked forward to a coming Saviour.
God answered this prayer when Jesus Christ came into the world, taking in human form, living among us, suffering as we suffer, and bearing our sins upon the Cross. He was raised to new life as the firstfruits of the resurrection to come, and it is through Jesus Christ that forgiveness of sins and everlasting life are promised and freely given to all who ask for it.