Why is electrical tape called electrical tape

The electrical operation on the Berlin S-Bahn
Volume 2.1: The Great Electrification - 1926 to 1930
2015; 160 pages, many illustrations, format 30.5 x 21.5 cm; bound
Without waiting for the results of the electrical operation on the northern routes, the administrative board of the DRG approved the electrification of the Berlin city, ring and suburban railways at its Hamburg meeting from July 6th to 8th, 1926. The "Great Electrification", as this construction project was called, should be carried out more quickly in order not to lose passengers to the constantly modernized means of transport of the urban BVG. On June 11, 1928, electric car trains in a new color scheme ran for the first time on the Stadtbahn between Erkner and Potsdam, with fully electric operation on the Ring from May 15, 1929, the "Great Electrification" was completed. The electrically operated network was supplemented with the commissioning of the Jungfernheide-Gartenfeld lines, the so-called Siemensbahn, and Kaulsdorf-Mahlsdorf.
In a very short time, the German wagon construction industry had designed a new type of wagon based on the 1925/26 design. With a number of 1,276, which is still unique today, the type of wagon known as the "Stadtbahner" had a lasting impact on the railroad landscape and the Berlin cityscape until the end of the millennium. The electric Stadtschnellbahn was given a uniform name in 1930. Since that year, a white "S" on a green background has been pointing to the S-Bahn stations of the electric Stadtbahn. The task of this book on the S-Bahn chronicle is to describe the history of the changeover of the Berlin Stadtbahn from steam to electric traction in all its facets.