Why do keetins hiss?
Most sounds a cat of any age makes means that they are either angry or scared (purr usually excluded)
So if your kitten is hissing i sugest that you stop hurting/scaring it.
'Hiss' is an onomatopoeia, often describing the sound of air escaping. The snake made a loud hiss and raised up it's head, ready to strike. First a pop, then a sharp hiss, 'NO!' he exclaimed, 'Not another flat tyre!' The cat made a hiss when we entered the room. The oil in the frying pan began to crackle and hiss, so we knew it was time to add the bacon.