Isidore of Seville, Etymologies 8.6.11-14
‘Academics’ are so called from the home of Plato, the Academy in Athens, where Plato used to teach. They thought that all things were uncertain; but, as we must confess that there are many things uncertain and hidden which God willed to exceed human intelligence, nevertheless there are many things which can be taken in by the senses and comprehended by reason. Arcesilaus of Cyrene established this sect. Democritus was a follower of it, and he said that just as in a deep well there may be no bottom, so too the truth lies hidden in the depths.
The Peipatetics were so called from the habit of perambulation, because their originator Aristotle was in the habit of arguing while he walked. They hold that a certain particle of the soul is eternal: most of the rest is mortal.
The Cynics are so called from their filthy shamelessness. For, against human decency, their habit was to have sex with their spouses in public, reckoning that it was right and noble to lie down with one’s wife in the open, because marriage is a just thing, and saying that it should be done it public as by dogs in the streets and fields. Thus they receive their appellation from the dogs whose lives they imitate.
Academici appellati a villa Platonis Academia Athenarum, ubi idem Plato docebat. Hi omnia incerta opinantur; sed, sicut fatendum est multa incerta et occulta esse, quae voluit Deus intelligentiam hominis excedere, sic tamen plurima esse quae possint et sensibus capi et ratione conprehendi. Hanc sectam Arcesilaus Cyrenaicus philosophus repperit; cuius sectator fuit Democritus, qui dixit tamquam in puteo alto, ita ut fundus nullus sit, ita in occulto iacere veritatem.
Peripatetici a deambulatione dicti, eo quod Aristoteles auctor eorum deambulans disputare solitus esset. Hi dicunt quandam particulam animae esse aeternam: de reliquo magna ex parte mortalem.
Cynici ab inmunditia inpudentiae nuncupati. Contra humanam enim verecundiam in propatulo coire cum coniugibus eis mos erat, censentes licitum honestumque esse palam cum uxore concumbere, quia coniugium iustum est, publice id praedicantes agendum, ut canes in vicis vel plateis. Vnde et a canibus, quorum vitam imitabantur, etiam vocabulum nomenque traxerunt.