Copper gets its name from the island Cyprus, due to its association with Venus. Venus was born on the island and copper was sacred to her.
Copper is very soothing, reduces inflammation, ease conflicts and helps to overcome problems, finding a positive outcome.
From The Essential Crystal Handbook, by Simon and Sue Lilly:
Irritation, mood swings, tension and insomnia can be caused by the movement of the sun, moon and planets. If you are feeling a little 'off' for no apparent reason, carry or wear some copper or put some under your pillow. If your state improves, then you can be fairly sure that planetary movements were a contributing cause.'