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