PICTURE CREDIT http://tomsaleebastravels.blogspot.com/
It is generally assumed that Roti Canai got its name from Chennai, the capital of Tamil Nadu.
So did Roti Canai really get its name from Chennai?
PICTURE CREDIT http://www.yamu.lk/place/chennai/
Parotta may have entered India via North India or via Kerala. Because Kerala is exposed to the Arabian Sea and many traders from Middle East used to trade in Kerala.
There is also another theory that suggest that the main ingredient to make Parotta, the Maida flour, was introduced to South India only during WW2. Maida flour is a wheat flour and wheat was first cultivated in the Middle East.
I am not very sure about the authenticity of such theories but the Middle East-Kerala theory makes more sense.
We are not sure who introduced Parotta in Malaya (now Malaysia). It could have been the Tamils or Malayalees, it could have also been others from India or even someone from the Middle East.
The Malays had several words for metal works. When working on the metal, the blacksmith will hammer the metal, flatten it, then cut into half, forge it, hammer it, flatten it, then cut into half....the process is repeated.
This process is known as canai in the Malay language.
Similarly, the cook who prepares the Roti Canai will smash the dough, spread it, fold it into half, smash it, spread it, fold it into half.....the dough takes a beating similar to the metal in a blacksmith's workshop.
This is how Parotta became Roti Canai in Malaysia. Instead of a layered piece of round bread like the Parotta, we made our Roti Canai appear folded.
This is the story of Roti Canai and it has got nothing to do with Chennai because back in the olden days, Chennai was known as Madras.
(The origin of Madras or Chennai can be read at the links below)
Dr.Jayabarathi's input on the word Canai having a Tamil origin. As mentioned, it is not a corrupt form of Chennai. It is the process of beating the dough.