Ethernet got its name from luminiferous ether , an old physics idea that light waves needed a medium to travel through; Robert Metcalfe chose it because he wanted to suggest a network medium that could carry signals over many kinds of cabling.

Why the name fits

Metcalfe’s idea was that the network layer should be medium-agnostic, able to run over coax, twisted pair, radio, optical fiber, or even power lines, and “ether” captured that flexible, all-purpose carrier concept.

Common confusion

People often mix up Ethernet with RJ45. RJ45 is a connector term from telephone standards, while the plug most people use for Ethernet is technically an 8P8C modular connector that got mislabeled over time.

In plain terms

So the name does not come from the physical connector itself; it comes from the networking concept and the old “ether” metaphor for something that carries signals through a shared medium.

TL;DR: Ethernet is named after the obsolete physics “ether” idea, not after the connector.