Sir, there are numerous versions as to the origin of the names of Chennai/Madras: Here is an excerpt from Wikipedia which deliberates on a few:
The name Chennai, is a shortened form of Chennapattanam, the name of the town that grew around Fort St. George, which was built by the English in 1639. There are two versions about the origin of the name Chennapattanam: According to one version, Chennapattanam was named after Damarla Chennappa Nayakudu, Nayaka of Kalahasthi 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...
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the English East India Company. According to the second account, Chennapattanam was named after the Chenna Kesava Perumal Temple; the word chenni in Tamil means face, and the temple was regarded as the face of the city.
The city's former name, Madras, is believed to have been derived from Madraspattinam, a fishing village north of Fort St. George, where the administrative HQ is located. Other arguments suggest that the Portuguese who arrived in the area in the 16th century had named the village Madre de Deus, meaning the Mother of God. Another possibility is that the village's name came from the prominent Madeiros family of Portuguese origin, which consecrated the Madre de Deus Church in the Santhome locality of Chennai in 1575. It is uncertain whether the name 'Madraspattinam' was in use before European influence. Another theory concludes that the name Madras was given to Chennapattanam after it was taken from a similarly named Christian priest, while other parties are of the opinion that it might have been taken from a fisherman by the name of Madrasan, or from religious Muslim schools which were referred to as Madrasas, or the word Madhu-ras, which means honey in Tamil. After the English gained possession of the area in the 17th century, the two towns, Madraspattinam and Chennapattinam, were merged, and the English referred to the united town as Madrasapattinam. The state government officially changed the name to Chennai in 1996, at a time when many Indian cities were being renamed.