If you Google "DIN Diode Jack" - you'll find jacks and cables so referenced, specifically one being a German site. (and Germany is where the nomenclature for DIN was established)
Since there are multiple 5 pin DIN pin arrangements of the same diameter, "Diode" was probably understood to mean the 180 degree pin arrangement, or used to ID how the pin's were connected to the RCA jacks.
Last edited by Rob Grabon on November 3, 2018 16:01.