I had always assumed that Aristotle titled his own works. But under the Wikipedia article on Metaphysics, it gives an alternative explanation for the origin of the work's title:
Subsequent to the arrangement of Aristotle's works by scholars at Alexandria in the first century CE, a number of his treatises were referred to as τὰ μετὰ τὰ φυσικά (ta meta ta fysika; literally, "the [writings] after the Physics"). This is the origin of the title for collection of treatises now known as Aristotle's Metaphysics. Some have interpreted the expression "τὰ μετὰ τὰ φυσικά" to imply that the subject of the work goes "beyond" that of Aristotle's Physics or that it is metatheoretical in relation to the Physics. But others believe that "τὰ μετὰ τὰ φυσικά" referred simply to the work's place in the canonical arrangement of Aristotle's writings, which is at least as old as Andronicus of Rhodes or even Hermippus of Smyrna.
That whole passage has a citation to one book to which I don't have access:
- W. D. Ross, Aristotle's Metaphysics (1953), vol. 1, p. xxxii.
It seems to be implied here that Aristotle didn't title Metaphysics himself, if the source is to be believed. Does this mean that all the titles of Aristotle's works, Poetics, Metaphysics, Rhetoric, On the Soul, etc., were actually not titles explicitly denoted by Aristotle, but chosen by scholars arranging his work at the library of Alexandria?
To provide some context, this subject is of interest to a question on the English Language & Usage Stack Exchange: Why do the titles of scholarly works sometimes begin with the word “on”?