The term ipse dixit is the Latin equivalent of the Greek autos epha,
referring to Pythagoras, as in, The master (Pythagoras) said it so it must
be true and no proof is needed. In our modern world, this has many forms:

Child: Why do I have to go to bed at eight every day?
Parent: Because I said so.

Employee: Why do we have to do this project if it's going to be scrapped anyway?
Boss: Because I said so.

An appeal to authority also known as argument from authority, argumentum ad verecundiam (Latin: argument from modesty) or ipse dixit (Latin: he himself, said it), is one method of obtaining propositional knowledge.