Abstract: We make a popular introduction to the gauge theories in physics，and then we discuss the origin of the word“gauge”used in physics. Originally，gauge means ruler or calibration standard. The use of“gauge”in classical electromagnetism started after Hermann Weyl had presented the gauge theory of a quantum charged particle coupled with an electromagnetic field in 1928 ～ 1929. If Weyl had not made a failed attempt in 1918 ～ 1919，trying to deduce electromagnetic vector potential through the scale change induced by parallel transport in spacetime， there would not have been the use of the word“gauge”for electromagnetic vector potential. We also review the contributions of Schrdinger，Fock and London.

Key words:  gauge, electromagnetism, quantum mechanics, Yang - Mills theory