1879, from Latin optimum, neuter singular of optimus "best, very good" (used as a superlative of bonus "good"), perhaps (Watkins) related to ops "power, resources" (in which case the evolution is from "richest" to "the most esteemed," thus from PIE root *op- "to work, produce in abundance"); or perhaps it is related to ob "in front of" (de Vaan), with superlative suffix *-tumos.
In English the word was used originally in biology, in reference to "conditions most favorable" (for growth, metabolic processes, etc.). As an adjective, "best or most favorable," from 1885.
"government by the nobles or upper classes," 1590s, from Modern Latin optimatia, from Latin optimas (plural optimates) "belonging to the best or noblest," in plural, "aristocrats," from optimus "best" (see optimum).
1759 (in translations of Voltaire), from French optimisme (1737), from Modern Latin optimum, used by Gottfried Leibniz (in "Thodice," 1710) to mean "the greatest good," from Latin optimus "the best" (see optimum). The doctrine holds that the actual world is the "best of all possible worlds," in which the creator accomplishes the most good at the cost of the least evil.
En termes de l'art, il l'appelle la raison du meilleur ou plus savamment encore, et Théologiquement autant que Géométriquement, le systême de l'Optimum, ou l'Optimisme. ["Memoires pour l'Histoire Des Sciences & des beaux Arts," (Journal de Trévoux), Feb. 1737]
Launched out of philosophical jargon and into currency by Voltaire's satire on it in "Candide." General sense of "belief that good ultimately will prevail in the world" first attested 1841 in Emerson; meaning "tendency to take a hopeful view of things" first recorded 1819 in Shelley.
Proto-Indo-European root meaning "to work, produce in abundance."
It forms all or part of: cooperate; cooperation; copious; copy; cornucopia; hors d'oeuvre; inure; maneuver; manure; oeuvre; office; official; officinal; omni-; omnibus; omnium gatherum; op. cit.; opera; operate; operation; operose; optimism; optimum; opulence; opulent; opus; Oscan.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit apas- "work, religious act," apnas- "possession, property;" Hittite happina- "rich;" Avestan huapah- "doing good work, masterly;" Latin opus "a work, labor, exertion;" Greek ompne "food, corn;" Old High German uoben "to start work, to practice, to honor;" German üben "to exercise, practice;" Dutch oefenen, Old Norse æfa, Danish øve "to exercise, practice;" Old English æfnan "to perform, work, do," afol "power."