Chennai is also known as Chennapattanam. The town grew around Fort St. George, which was built by English in 1639.
The origin of the word "Chennai" has a number explanations. There are so many researches that claim the word to be of Tamil origin and recent research disputes it as Tamilised version of a Telugu word.
Three different aspects explain the origin of the name Chennai/Chennapattanam:
First theory explains the name that it was from the Telugu ruler Damarla Chennappa Nayakudu, Nayaka of Chandragiri and Vandavasi, father of Damarla Venkatadri Nayakudu, from whom the English acquired the town in 1639. The first official use of the name Chennai is said to be in a sale deed, dated 8 August 1639, to Francis Day of the East India Company.
the second theory states it was named after the Chenna Kesava Perumal Temple; the word chenni in Tamil means face, with the temple regarded as the face of the city.
Historian J B Prashant More has stated that the origin of the name "Chennai" is Telugu and not Tamil.