"Did you know why the ring is worn on the left hand? It is because this if the hand closest to the heart. Also, the placement on the third finger, as in Western tradition, comes from the Greeks, who believed that the third finger was connected directly to the heart by "the vein of love". And it was in Rome that rings came to be made of gold, symbolizing unending love and commitment."
So the rings are worn on the left hand to be closest to the heart. Many women wear their engagement rings before they are married on the right hand and then move it to their left. It signifies the transition, the marriage commitment and eternal heartfelt devotion.
Having said that, German Protestants wear their wedding rings on their right hands!
Engagement rings, often known as betrothal rings, hail from the ancient days of marriage when men would purchase their brides and when gold rings were circulated as currency. The groom-to-be would offer his bride-to-be a gold ring both as his partial payment and as a symbol of his intentions.
The women in earlier times wore woven bands made of rush (a flexible marsh plant with hollow stems), and replaced them each year. Future Roman brides wore rings made of iron to symbolize the permanent, unending nature of marriage. During Medieval times, the groom-to-be placed the ring on three of the bride's fingers in turn to represent the Holy Trinity -- the Father, the Son, and the Holy Spirit.
What's interesting is the gimmal ring, which originated during the Elizabethan period and is a set of three interlocking rings. During the engagement, the future couple, and their witness each wore one of the rings until the wedding day when the three pieces were united as a single ring for the bride. The three part ring had two clasped hands on it. Copen Cabana DJ and Custom Wedding Photo Book Services http://www.knowareland.com