A Cnoön is an entity of the Hylaean Theoric World. Common generalizations include geometric shapes such as isosceles triangles. Cnoöns do not include natural constants such as the speed of light that vary from universe to universe and result in the differences between the Geometers and Arbreans.
Given the introduction's definition for the use of dieresis ("gets a syllable all its own"), "cnoön" may be pronounced like "know-on", which would make it an awesomely terrible pun name for a discrete particle of knowledge.
In Arabic, a canon of science or mathematics is referred to as a al-Qānūn, "ka-noon", which "cnoön" may be referencing. (See Avicenna’s The Canon of Medicine, a translation of the Arabic title القانون في الطب (al-Qānūn fī aṭ-Ṭibb), with "Canon" (Translated in English to "Law") used in the sense of "law".
Cnoöns seem identical to Plato's Theory of Forms.