EKG (also called ECG) is short for electrocardiogram. Electro refers to the heart's natural electrical activity, which the test records through small wires taped on your chest. (Don't worry, you won't feel a thing.) This video shows what it's like.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
Children's Hospital of Orange County | 
University of California, Irvine