What is the name of the first Computer Network?

The computer itself is the first computer network, ARPANET was the first computer to computer network over a link.

ARPANET (Advanced Research Projects Agency Network) is the first computer to computer link created in 1969.

السلام عليكم ورحمة الله وبركاته

the two early Ethernet specifications, 10BASE5 and 10BASE2. These two Ethernet specifications defined the details of the physical and data link layers of early Ethernet networks.

The Ethernet consists solely of the collective Ethernet NICs in the computers and the coaxial cabling. 

The basic logic of an old Ethernet 10BASE2 network, which uses a single electrical bus, created with coaxial cable and Ethernet cards.

Because the network uses a single bus, if two or more electrical signals were sent at the same time, they would overlap and collide, making both signals unintelligible.