Mater misericordiae (Mother of Mercy)
The title "Mother of Mercy" is familiar to most of us from the well-known Salve Regina, in which Mary is addressed as our Queen and Mother of Mercy.
Note that this is the chant used by Dominicans, and is completely different from the Gregorian version often found in parish hymnals, etc.
Why do we call Mary our "mother of mercy"? It is a fitting title, because she was completely human, and yet born without Original Sin, thanks to the foreseen merits of her son Jesus. Mary could see all the flaws and faults of the rest of humanity, and look upon these with mercy and compassion, not because she had personal knowledge of these things, but because her sinless nature gave her the privilege Adam and Eve lost when they ate the forbidden fruit in the Garden of Eden: she always knew the right way to act, and she did so. Her will was perfectly aligned with the will of God. Just as God has mercy on all His children, always drawing them to repentance when they sin, Mary too is merciful. She is not God's equal, but she is the most powerful intercessor with God that we have. Thus, in this time when many would rather pursue what they believe to be justice rather than show mercy toward their fellow flawed human beings, Pope Francis made a wise decision in adding this petition to the Litany of Loreto.
Mary, Mother of Mercy, pray for us!