(Wikipedia says “In the UK, the terms jack plug and jack socket are commonly used for the respective male and female phone connectors. In the US, a stationary (more fixed) electrical connector is called a jack .” and mentions that “jack” comes from a 1880’s patent. I just looked at that, and it’s for a “cut-out or spring-jack switch” mechanism where the signal is automatically grounded when nothing’s plugged in. So “jack” refers to the switch mechanism, not the plug, and you’re all wrong 
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