Dear Michael:

The wedding ring does have pagan origins. But, my response to your commenter is "so what." The Cross is a symbol with pagan origins, too. Even the idea of a propitiatory sacrifice for sins has a pagan origin. There is nothing wrong with taking pagan symbols and Christianizing them. The point is that they have been "Christianized".

One reason why the pagans came up with ideas that are very similar to the symbols and ideas we have in Christianity is because those pagan peoples had a primitive idea of God and knew instinctively that practices, such as sacrifice, had to do with God somehow. St. Paul tells us that the basic knowledge of God is written on the hearts of all human beings (Roman 2:14-16). This knowledge is genetic, as-it-were. But, the pagans did not have the benefit of Divine Revelation as we do to properly interpret this inherent knowledge. This is why many things in the Christian faith have similarities with the imperfect understandings of things similar among the pagan peoples.

As for a history of the wedding ring, there is a website that goes into detail on this, called Wedding Ring Origins. Here is an excerpt:

It was the ancient Egyptian who established the custom of placing a ring on the finger of his wife, as a sign that he had confidence in her ability to care for his house. The Greek and Roman bridegroom often gave a ring to the bride's father-a practice that was probably a survival of primitive bride purchase. In the second century B. C., the Roman bride was presented with a gold ring. But this she wore only in public. Such a ring was much too precious to wear while tending to household duties; and so the groom gave the bride a second ring - for use in the home - which was usually made of iron and had little knobs in the form of a key. Of course, these "key" rings were weak and could open only those locks requiring very little force to turn, but their significance, in that the wearer had the right to seal up the giver's possessions, was strong.

Probably the most imposing ring of all time was that used at the Hebrew wedding. This curious ring was shaped like the roof of a Jewish temple, and was so large and clumsy that it could not be worn in the ordinary manner. Many times it was the property of the synagogue and was borrowed for the event, for it was needed during only a portion of the ritual and was then removed. It has even been said that these huge, elaborate rings were used to hold myrtle branches at weddings.

It was not until about 860 that the Christians used the ring in marriage ceremonies, and then it was not the plain circlet that we now use, but a highly decorated device, engraved with symbolical figures of doves, lyres and even of two linked hands. Such a "Heathenish" gadget was not given a hearty reception by the Church, and for a long time its use was discouraged, though never completely abandoned.

...

We cannot be sure exactly how the custom of placing the marriage or betrothal ring on the third finger of the left hand arose. It may be ascribed to the belief of the ancients' that a special vein or nerve ran directly from this finger to the heart. Then, too, it was said that this particular combination was most suitable for finery, as the left hand was used less than the right and the third finger would better protect the ring from injuries, inasmuch as it could not be "extended but in company with some other finger." Still another explanation centers about the idea of the left hand denoting subjection of wife to husband. In the Christian Church service, the priest touched three consecutive fingers, saying, "In the name of the Father, of the Son, and of the Holy Ghost," and placed the ring on the last finger touched.

God Bless,
Bro. Ignatius Mary