CON1 to USB connector cable
CON1 undoubtedly stands for Connector 1, which is an arbitrary label on the board used to refer to the given connector. It has no specific meaning outside of "This is the first connector", in the same way R1 is used for the first Resistor, Q1 for the first Transistor, TP1 for the first Test Point, etc.

Seeing the picture that the OP provided in the comments, this is the most obvious answer.