I think it is called an older Dravidian language, and not Tamil because the older Dravidian language cannot be called Tamil. It is vastly different from the Tamil that is spoken today. Calling a language the "oldest" is usually just veiled attempts at asserting racial/cultural superiority that does not really exist. Oscar Tay has a great answer on Quora explaining this, and I cannot state it any better: https://www.quora.com/Is-Tamil-the-oldest-living-language-in...