The Greek word peirar means “end, limit” and peras means “end, limit, boundary”. The word a-peiron is the negation of these meanings. In Hesiod and other classical Greek texts peras mainly describes the end of the known world.Anaximander (c. 610 - c. 546 BC) introduced “the abstract apeiron (indefinite, infinite, boundless, unlimited) as an origin of the universe, a concept that is probably influenced by the original chaos (gaping void, abyss [having no bottom], formless state) of the mythical Greek cosmogony from which everything else appeared.” (http://en.wikipedia.org)

Karl Popper quotes a fragment from Xenophanes’ (6th century BC) that shows the transition from chaos to apeiron: “The upper limit of earth borders on air. The lower limit reaches down to the unlimited (i.e. the Apeiron).” (Karl. R. Popper, The world of Parmenides. New York: Routledge, 1998; p. 39)