What is the correlation between Cardano and ETC?
IOHK is the developer for ETC and the primary developer for Ada (along with many others).
Here is some back story Google for more:
Hoskinson co-created Ethereum. He left prior to the DAO hack but was ideologically very opposed to the ethereum community essentially reversing what had happened by hard forking. A decent amount of miners shared this view and continued on the original chain. Eventually Hoskinson’s company IOHK got involved with helping to develop ETC. IOHK is also the company contracted to develop Cardano through 2020.