[rayiner]

Our engagement rings trace back to Middle Ages Europe, where they arose to serve a notice function (this person is taken). Diamonds became associated with them in the Victorian era, and became more widespread when ordinary people started copying the trappings of nobility (diamond engagement rings, college, etc.).

[slfnflctd]

I was told a story that the concept originated before this, as a subtle way to identify acolytes of a certain religious order or place of worship in ancient times. The phrase used was "temple prostitutes". I've searched a bit and had trouble finding a source to back this up, though. If anyone has one or can debunk it, I'd be happy either way.