Chennai Areas Etymology (1/n)
Avadi - Armoured Vehicles and Ammunition Depot of India
Adyar - Banks of Adaiyaaru
developed during TNHB reign
Ashok Nagar - After the famous Ashoka Pillar.
Ayanavaram - Ayan means "The one", due to a shiva temple situated in the area #Chennai

Besant Nagar - After Annie Besant
Chetput - Named after a Chetty Zameen who ruled here, originally known as Chettiyar Pettai which was shortened by the British (Credits: Sridhar Radhakrishnan)
Chindadripet - Chinna Thari Pettai, due to the weavers population in the locality

Chinna Malai (Little Mount) - After Dheeran Chinnamalai, the valiant tamilian.
Chromepet - After the old Chrome factory
Egmore - The land of the rising sun. (Anglicized from Ezhumboor) Higher Mean sea level than the other places in Old Madras. There is a Shiva temple here!!

Guindy - After the Guindy (Rammer) which Bringi Maharishi planted in this place to begin a great Yaha (Sacrifice) against Goddess Parvati
JJ Nagar - After ADMK party chief J.Jayalalitha.
Kodambakkam - After Karkodagan, the mythical snake which worshipped Shiva who has a temple

Koyambedu - After the Ashwa medha yagam done by Lord Rama, his sons Luv and Kush tied the horse in Koyambedu. Koyam means horse in Sanskrit.
KK Nagar - After Kalaignar Karunanidhi and was developed during his reign
Mambalam - Maha Vilva Trees.

Mandhaveli - Mandhai means herd and Veli means space. Must have been herdland previously.
Mylapore - Mayil means peacock. The goddess Parvati is said to worshipped Lord Shiva in the form of a peacock here, to get absolved of a sin. So, Mayilapuram (puram meaning city)

Nandhanam - Previously Gambier's gardens, was renamed by Rajaji as a part of creating Greener Chennai. Nandhanam means Garden. And apparently the name of the Tamil year "Nandana"
Nanganallur - Nangai Nallur/ Thillai Ganga Nagar, coined by Kanchi Shankaracharya

Parrys - Named after a merchant Thomas Parrys who estabished it as a trade center.

Perambur - After Pirambu trees in the locality

Pondy Bazaar - After Soundarapandian.

Poonamalee - Poo Irundha Alli, abundance of Jasmine.

Porur - Por means war. Believed to be a battlefield since ancient times. Contans the Arcot road which connects the Arcot Nawab with the capital. Home to a chola temple, etc.
Purasaiwakkam - Due to the Purasai trees
Royapettah - Nawab of Arcot were there Rayars of this district

Saidapet - Named after Sayyid Shah, the loyal general of the Nawab of Arcot who gifted this area.
Sowkarpet- after the Sahukars who settled there
Teynampet - Due to abundance of the Cocnut trees in the region
T.Nagar - After Sir PT Thyagaraya Chetty

Thiruvanmiyur - Named after Valmiki
http://Thiru.Vi .Ka Nagar - Named after Thiru. Vi.Kalyanasundaranar, the prolific tamil writer
Thirisoolam - Home to Thirisoolanathar temple on the hill.
Thondaiyarpet - Coined by Masthan Sahib after his birthplace Thondi.

Thousand Lights - Derives its name from the thousand lights that were lit when an Indian National Congress Annual Session was held for the first time in Madras

Triplicane - Thiru Alli Keni, Pond with the Alli flowers: Parthasarathy temple tank.
Vadapalani - Palani in the North, after the famous Murugan temple
Vandalur - Derives its name from Vandal, which is the sediments from a river.

Velacherry - Evolved from Vedasreni, the place of worship of the four vedas.
Villivakkam - Real name - Vilvaaranyam. A very old Shiva temple is situated here. Built by sage Agasthiyar. A lot of Vilvam trees were found there. Hence it got the name Vilva Aaranyam.