What does the name 'Mercy' mean?

Mercy is one of a number of names (Hope, Faith, Charity, Prudence etc.) which derive from a virtue. Mercy is a virtue closely allied to compassion. It is that virtue which makes you hold your hand when you are in a position to cause someone harm, or to go out of your way to help someone when there is no benefit to yourself. You may be in a position to ruin someone's reputation by revealing their secret, or turn them out of their home because you hold their mortgage and they have defaulted, or watch them be run over by a car, but if you have mercy you will not reveal their secret or take their house and you will warn them about the oncoming car or even push them out of the way, in order to avoid hurting them.