Malayalam is the language of natives of KeralaKerala State was formed in 1956 on the basis of a decision by the Government of India to forms States on the basis of regional languages. When in an area, a particular language is spoken by the majority, all such areas will be brought under the same State. Thus when Kerala state was formed it was by combining those areas where Malayalam was spoken by the majority. Portion of Tamil Nadu (then Madras State), Kochi and Travancore got joint and the new State came into being.
As mentioned the people belonging to this newly formed State are having Malayalam as their mother tongue. But if you travel from Kasargod (northernmost district of Kerala)to Thiruvananthapuram (Southern district) you can hear different slang of Malayalam. Very often, different to the extent that even a 'Malayalee' cannot follow it completely. Hence it will be interesting to make discussion on this issue.