When আপনি curse, it means আপনি don't have any word(s) to say that are appropriate for the siuation you're in.When আপনি see people cursing,you think"that person doesn't have anything to say but curse words" and আপনি think it's funny.Another theory is that দ্বারা who it is.Ex:When আপনি see an old lady আপনি think she's nice and sweet and gentle.And then she starts cursing and আপনি think it's funny.