late Old English plaster "a medicinal solid compounded for external application," from medical Latin plastrum, shortened by loss of the original prefix from Latin emplastrum "a plaster" (in the medical as well as the building sense), from Greek emplastron "salve, plaster" (used by Galen instead of the more usual emplaston), noun use of neuter of emplastos "daubed on," from en- "on" + plastos "molded," verbal adjective from plassein "to mold" (see plasma).
The use in reference to the material composed of lime, water, and sand (with or without hair for binding), used for coating walls, is recorded in English from c. 1300, via Old French plastre, from the same source, and in early use the English word often had the French spelling. The meaning "gypsum" is from late 14c.; plaster of Paris "powdered calcinated (heat-dried) gypsum," which sets rapidly and expands when mixed with water(mid-15c.) originally was made from the extensive gypsum deposits of Montmartre in Paris. Plaster saint "person who makes a hypocritical show of virtue" is by 1890.
early 14c., "to cover or overlay (walls) with plaster;" late 14c., "to coat with a medicative plaster," from plaster (n.) and partly from Old French plastrier "to cover with plaster" (Modern French plâtrer), from plastre. Figurative use, "to load to excess" (with praise, etc.), is from c. 1600. Meaning "to bomb (a target) heavily" is first recorded 1915. Sports sense of "to defeat decisively" is from 1919. as an adjective, plastered is from late 14c. as "coated with plaster." The slang meaning "very drunk" is attested by 1912.