Neapolitan expression used to swear against ancestors, in short, the dead relatives of the person to whom it is directed.
And that’s not all because, besides ” chitemmuort ” there is also ” chitestrammuort “, a more modern word that makes the meaning even better...
‘Nonnna I’ve putted pineapple on the pizza, is it ok?’
‘Mannaggia a chitemmuort, you want to kill me’