Shri JBP More is a scholar in history with a doctorate in South Indian history. In his interview given to Rediff.com he has contended that Chennai is not a Tamil but Telugu word. Madras is a Tamil name and the name was wrongly changed to Chennai under the impression that it was a British name. Here is the link to the interesting interview.
'There's no word like Chennai in Tamil' - Rediff.com India News
'There's no word like Chennai in Tamil' - Rediff.com India News