encyclopedia (n.) Look up encyclopedia at Dictionary.com
1530s, "general course of instruction," from Modern Latin encyclopaedia (c.1500), thought to be a false reading by Latin authors of Greek enkyklios paideia taken as "general education," but literally "training in a circle," i.e. the "circle" of arts and sciences, the essentials of a liberal education; from enkyklios "circular," also "general" (from en "in;" see in + kyklos "circle;" see cycle (n.)) + paideia "education, child-rearing," from pais (genitive paidos) "child" (see pedo-).

Modern sense of "reference work arranged alphabetically" is from 1640s, often applied specifically to the French "Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts, et des Métiers" (1751-65). Related: Encyclopedist.