It's orgin is the country of Moab, from ancient times (present day I believe is in Jordan, where the Dead Sea is). In the Bible it tells of a Hebrew family who left home due to famine. The family dies of an illness except the mother and her two D-I-L's. One chose to return to her family, the other one, Ruth, chose to go with her M-I-L.
Ruth is important to Christians for two reasons. The famous line in Christian beliefs is (modernized): "where you go I will go, your people will be my people, your GOD will be my GOD". Through her line is David and then on to Jesus.
So, Ruth is a female name of Moab origin, but became an impotant name to Hebrews and then Christians, thus it popularity.
Hope that helps.
On a side note
If I offend anyone on religious info I apologize. I am giving facts from the Christian bible about the name of Ruth. My personal beliefs, each person's religious beliefs, whatever they are, should be private. Freedom of religion is the fundamental right of each peson of my home country, USA. Again, I am sorry if I offended, that is not my goal.
In the area of names, what about Care Less? that could use fit some traits.
Edited: I realized that I had typed couple, it was a family of four, parents and two sons.