What is the origin of the symbol Cu for Copper?
Copper
Copper is a chemical element with symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.
Planet symbols
The Venus symbol (♀) consists of a circle with a small cross below it. 
It originates in Late Antiquity as an astrological symbol for the planet Venus (associated with the goddess Venus), and hence as alchemical symbol for copper. In modern times, it is still used as the astronomical symbol for Venus, although its use is discouraged
by the International Astronomical Union.