An unusual mondegreen. In this beautiful song, music director Pritam has packed the chorus' singing of 'salaamaa' - an Arabic word of significant religious meaning and in this context, likely meant as 'may you live in peace', or simply 'greetings' - so tightly together and rhythmically fast, that after one or two occurences, it blends into the ear as 'massaalaa, massaalaa'. Not only a phonetic palindrome of the original term but ironically, one of the words of the film's title. Check it out.