Where does “ⲑⲣⲟⲛⲟⲥ” come from?

ⲑⲣⲟⲛⲟⲥ (Coptic) comes from Ancient Greek θρόνος, from Proto-Indo-European dʰer- — to support; to hold.

ⲑⲣⲟⲛⲟⲥ (Coptic): throne, seat of a person in power