mid-14c., "specially prepared or arranged display," from Old French spectacle "sight, spectacle, Roman games" (13c.), from Latin spectaculum "a public show, spectacle, place from which shows are seen," from spectare "to view, watch, behold," frequentative form of specere "to look at" (from PIE root *spek- "to observe").
1540s, "a tract or region of the earth," shortening of climate (or a nativization of Latin clima). It might usefully take up the old, abandoned "horizontal region of the earth" sense of climate, but it is used chiefly by the poets, and they display no evident agreement on what they mean by it.
1704, "of or pertaining to the use of fire" (a sense now obsolete); 1825, "of or pertaining to fireworks and the art of making them," from pyrotechny "the manufacture and use of gunpowder" (1570s), from pyro- "fire" + Latinized form of Greek tekhnē "art" (see techno-).
Figurative use, "brilliant, explosive display," is attested from 1847. Related: Pyrotechnical (1610s, from pyrotechny).
late 14c., "to spread" (one's fame), "to show plainly," from manifest (adj.) or else from Latin manifestare "to discover, disclose, betray." Meaning "to display by actions" is from 1560s; reflexive sense, of diseases, etc., "to reveal as in operation" is from 1808. Related: Manifested; manifesting.