ETC is the original Ethereum

Unaltered chain renamed ETC survived immutability

Ethereum Classic (ETC): However, not everyone agreed with the decision to reverse the hack. Those who believed in the immutability (the principle that blockchain transactions should not be altered) of the blockchain continued to support the original version of the Ethereum chain, which became known as Ethereum Classic (ETC).

Ethereum (ETH) supporters believe the hard fork was necessary to protect the ecosystem, while Ethereum Classic (ETC) supporters believe the original chain is the "real" one because it has not undergone any changes and stays true to the original principles of decentralization and immutability.