The question of what constitutes a supercomputer technically depends on what technologies are cutting edge in any given era—but it's all about throughput. The term "supercomputing" has a long history.

C. 2500 BCE: Sumerian abacus -- c. 700 BC: Scytale -- c. 150: Antikythera mechanism -- c. 60: Programmable robot -- c. 850: "On Deciphering Cryptographic Messages" -- c. 1470: Cipher disk -- 1613: ...