shellac n.

"hard outer covering," Middle English shel, shelle, from Old English sciell, scill, Anglian scell "seashell; eggshell," which is related to Old English scealu "shell, husk," from Proto-Germanic *skaljo "piece cut off; shell; scale" (source also of West Frisian skyl "peel, rind," Middle Low German schelle "pod, rind, egg shell," Gothic skalja "tile"), with the shared notion of "covering that splits off," from PIE root *skel- (1) "to cut." Italian scaglia "chip" is from Germanic.

Also in late Old English as "a coating or layer." The general sense of "protective outer covering of some invertebrates" is in Middle English (by c. 1400 as "house of a snail;" by 1540s in reference to a tortoise or turtle); the meaning "outer layer of a nut" (or a fruit considered as a nut) is by mid-14c. With notion of "mere exterior," hence "empty or hollow thing" by 1650s. The meaning "hollow framework" is from 1791; that of "structure for a band or orchestra" is attested from 1938. To be out of (one's) shell "emerged into life" is by 1550s.

Military use for "explosive projectile" is by 1640s, first of hand grenades, and originally in reference to the metal case in which the gunpowder and shot were mixed; the notion is of a "hollow object" filled with explosives. Hence shell shock, "traumatic reaction to the stress of battle," recorded by 1915.

Shell game "a swindle" is from 1890, from a version of the three-card game played with a pea and walnut shells.

"red resinous substance," 1550s, perhaps immediately from French lacce, displacing or absorbing earlier lacca (early 15c.), from Medieval Latin lacca. All these are from Persian lak, from Hindi lakh (Prakrit lakkha), from Sanskrit laksha "red dye," which is of uncertain origin.

According to Klein, it means literally "one hundred thousand" and is a reference to the insects that gather in great numbers on the trees and create the resin. But others say lakh is perhaps an alteration of Sanskrit rakh, from an IE root word for "color, dye" [Watkins]. Still another guess is that Sanskrit laksha is related to English lax, lox "salmon," and the substance perhaps was so called from being somewhat the color of salmon [Barnhart]. Also see shellac (n.).

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.