mid-13c., "flat sheet of gold or silver," also "flat, round coin," from Old French plate "thin piece of metal" (late 12c.), from Medieval Latin plata "plate, piece of metal," perhaps via Vulgar Latin *plattus, formed on model of Greek platys "flat, broad" (from PIE root *plat- "to spread"). The cognate in Spanish (plata) and Portuguese (prata) has become the usual word for "silver," superseding argento via a shortening of *plata d'argento "plate of silver, coin."
From 14c. as "armor made of sheets of metal." Meaning "table utensils" (originally of silver or gold only) is from Middle English. Meaning "shallow dish on which food is served at table," now usually of china or earthenware, originally of metal or wood, is from mid-15c. Meaning "articles which have been covered with a plating of precious metal" is from 1540s.
In photography, "common rectangular piece of glass used to receive the picture," by 1840. The baseball sense "home base" is from 1857. Geological sense "nearly rigid part of the earth's lithosphere" is attested from 1904; plate tectonics is attested from 1967. Plate-glass for a superior kind of thick glass used for mirrors, shop-windows, etc., is recorded from 1729.
1540s, "flat plate of metal," from French plateine, from Old French platine "flat piece, metal plate" (13c.), perhaps altered (by influence of plat "flat") from patene, from Latin patina "pan; broad, shallow dish," from Greek patane "plate, dish" (from PIE root *pete- "to spread"). From 1590s as "the flat part of a press which comes down upon the form and by which the impression is made." Hence, on a typewriter, "cylindrical roller or other surface against which the paper is held" (1890).
"oblong piece of metal," 1580s, from pig (n.1) on the notion of "large mass." In Middle English sow also was used of a mass or bar of lead (mid-15c.).
c. 1300, "cinch on a nail;" c. 1400, "short metal pin or bolt inserted through a hole at the junction of two or more metal pieces," the point then hammered broad to hold them together; from Old French rivet "nail, rivet," from river "to clench, fix, fasten," which is of uncertain origin; possibly from Middle Dutch wriven "turn, grind," and thus related to rive (v.). Or the English word might be directly from Middle Dutch.