The connector most people call RJ45 has roots in telephone technology from the 1970s. The familiar Ethernet plug is technically an 8P8C modular connector—eight positions and eight contacts.
The name “RJ45” originally referred to a specific Registered Jack telephone wiring standard, not simply the plastic connector itself. As twisted-pair Ethernet became common, especially with 10BASE-T in the late 1980s and early 1990s, the RJ45 name became attached to the Ethernet connector and stuck.
Today, nearly everyone—from technicians to manufacturers—calls it RJ45, even though 8P8C is the more technically accurate name for the connector.
It’s a great example of networking terminology surviving long after its original meaning changed.
The name “RJ45” originally referred to a specific Registered Jack telephone wiring standard, not simply the plastic connector itself. As twisted-pair Ethernet became common, especially with 10BASE-T in the late 1980s and early 1990s, the RJ45 name became attached to the Ethernet connector and stuck.
Today, nearly everyone—from technicians to manufacturers—calls it RJ45, even though 8P8C is the more technically accurate name for the connector.
It’s a great example of networking terminology surviving long after its original meaning changed.