The word is an ancient Egyptian verb meaning to come into being, to become, to be transformed. In the hieroglyphic script it is written with the beetle sign, and the same root gives the name of the god Khepri, the form of the sun associated with the morning and with self-generation. The Temple of Set transliterates it Xeper and pronounces it in its own way, and treats the first person form, I have come into being, as the whole of the teaching in three words.
The word entered the Temple through its founding document, the Book of Coming Forth by Night, which Michael Aquino set down in 1975 and presented as received rather than composed. The Temple regards it as the word of its aeon, in the sense that a magical current is held to be summed up in a single term that states what the period is for.
What is claimed for it is a specific reading of the grammar. Because the verb is in a completed form, the statement is not an aspiration but a report: the speaker has already begun, and the becoming is something being done rather than something awaited. The Temple insists that this makes Xeper a process and not a state, so there is no point at which a person has finished. That reading is the doctrinal foundation of everything else the Temple teaches, and it is presented as a practice rather than as a proposition about the universe.