Origin and history of occasion

late 14c., "occurring now and then," from occasion (n.) + -al (1) or from Old French ocasionel and directly from Medieval Latin occasionalis. Meaning "casual" is 1560s. Meaning "happening on or pertaining to a particular occasion" is from 1630s. Of furniture, etc., "adapted for use on special occasions," from 1749. Middle English had also occasionary "affording opportunity, favorable" (mid-15c.).

late 14c., "western part" (of the heavens or the earth), from Old French occident (12c.) or directly from Latin occidentem (nominative occidens) "western sky, sunset, part of the sky in which the sun sets," noun use of adjective meaning "setting," from present participle of occidere "fall down, go down" (see occasion (n.)). As a geopolitical term, sometimes with a capital O, always somewhat imprecise.

With the definite article, the west; western countries; specifically, those countries lying to the west of Asia and of that part of eastern Europe now or formerly constituting in general European Turkey; Christendom. Various countries, as Russia, may be classed either in the Occident or in the Orient. [Century Dictionary, 1895]