For the history of the concept of the “Classics” around the fourth through the second centuries BCE, I rely mainly on Rudolf Pfeiffer’s History of Classical Scholarship.  He takes note of a key word for this concept, krisis (the source of our word “crisis”), in the sense of “separating,” “discriminating,” “judging” (verb krinein) those works and those authors that were deemed worthy of special recognition and those that were not.  Those that were “selected” in this process were the enkrithentes, a term that corresponds to the later Roman concept of the Classics, the classici, who were authors of the ‘first class’, primae classis.  This classical principle of selectivity, where some things have to be excluded in order for other things to be included, is the basis for the modern usage of the word canon.  The Greek word for those who were engaged in the process of making these critical selections was kritikoi ‘critics’.
The Alexandrian Classical model, as formalized in the very concept of the Pinakes of Callimachus, makes it explicit that a holistic perspective is a prerequisite for the application of the principle of selection. 
This whole description of the Museum or Mouseion, the sacred space that contains the Library, abounds in traditional metonyms that reveal the connections of power, wealth, and prestige. These metonyms help explain the metaphors of comprehensiveness, completeness, and universality associated with the idea of the library as a Classical model: