Your ignorance is profound !
Your Indian Army itself uses the word "Madras" for the Madras. Sappers Regiment .
en.m.wikipedia.org
A little bit of history.
The Nawab of Arcot had a Madarasa on the coast where the now renamed city of Chennai stands. When the British East India Company took over that strip of coast to establish a trading post they named it after the Madarsa or Madras . The name Chennai was adopted relatively recently. The city was called Madras for 125 years at least. Indian Army records refer to the Madras sappers as Madrasis and both railway stations in Egmore and Central in Chennai were called
Madras Central and Madras Egmore.