ipse dixitip·se dix·it
Origin of ipse dixitL, he himself has said (it)
Origin of ipse dixitFrom Latin ipse dīxit he himself said (it) ipse he himself dīxit third person sing. perfect tense of dīcere to say
From Latin ipse (“himself”) dīxit (“he said”), third-person singular perfect active of dīcō (“say, speak”), meaning "he himself said it", a calque of Ancient Greek αὐτός (autos) ἔφα (epha). Originally used by the followers of Pythagoreanism, who claimed this or that proposition to be uttered by Pythagoras himself.
ipse dixit - Legal Definition