Tam: சென்னை c(h)eṉṉai
‘Chennappa’s Village’ [Madras] City/ Capital/ District, Tamil Nadu
From Tel: Chennappa Nayaka; and Tam: paṭṭiṉam, ‘coastal town’, ‘fishing village/hamlet’
The English East India Company acquired land (actually, a small fishing village and beach) at Madraspatnam in 1639 to build a fort and trading post. The official grant was authorised by two brothers, Venkata and Ayyappa, who were local Nayakas or governors of the Vijayanagar Empire. It was they who requested the new settlement be called Chennapatnam after their father, Damarla Chennappa, the Telugu Nayak ruler of Kalahasti and Vandavasi. Work on the fortifications started on April 23, St George’s Day 1640, which is why the new fortification and settlement was called Fort St. George.
Gradually, the settlements began to merge: the fort and factory of Madrasapatnam in the North; and Chennapatnam, the southern colony around the fort (now populated by Indian weavers and artisans).
So both names have a history going back to the 17thC: Madras being used officially until the name was changed in 1997 when Chennai became the official name.
The name ‘Madras’ has an obscure origin – it certainly is not English. Some suggest it was named after a ‘headman’ Madrasan; or a local Portuguese family (Madra, Madera or Madeiros); or a San Thomé church, Madre de Deus; or even madrasa Muslim schools.
Madras was the capital of Madras Presidency under the British and became the capital city of Tamil Nadu. It used to be one of the top four ‘metros’ in India. But, like Kolkata, it has been overtaken by Bengaluru and Hyderabad.
However, it is still India’s fourth largest urban agglomeration (by population) and:
“…there is little doubt that all of them, not to mention the rest of the subcontinent, owe much to the seeds of modern progress first sown in Madras. The first major settlement established by the British, Madras, laid the foundations on which modern India has grown” [Muthiah (2018)].
For related place names see Indian Place names and Tamil Nadu place names.

Chennai – bird’s-eye view SlowPhoton