Mallu is Indian slang for a person from Kerala . It actually refers to a person who is born in Kerala and speaks Malayalam .
The word is derived as a shortened form of the word Malayali . This word is a result of Information Technology revolution and it is used more during chat, online forums and webpages. The word is not specific to any particular Indian language.
Even though this slang is rarely used inside Kerala , it is used extensively in other parts of India to refer to Malayalis .