late 14c., scannen, "to mark off verse in metric feet, analyze verse according to its meter," from Late Latin scandere "to scan verse," originally, in classical Latin, "to climb, rise, mount" (the connecting notion is of the rising and falling rhythm of poetry), from PIE *skand- "to spring, leap, climb" (source also of Sanskrit skandati "hastens, leaps, jumps;" Greek skandalon "stumbling block;" Middle Irish sescaind "he sprang, jumped," sceinm "a bound, jump").
English lost the classical -d- probably by confusion with suffix -ed (compare lawn (n.1)). Intransitive meaning "follow or agree with the rules of meter" is by 1857. The sense of "look at point by point, examine minutely (as one does when counting metrical feet in poetry)" is recorded by 1540s. New technology brought the meaning "systematically pass over with a scanner," especially to convert into a sequence of signals (1928). The (opposite) sense of "look over quickly, skim" is attested by 1926. Related: Scanned; scanning.
1706, "a close investigation, an act of scanning," from scan (v.). The meaning "image obtained by scanning" is from 1953.
in zoology and ornithology, "of or pertaining to climbing, used for climbing," by 1789, from Latin scansorius "used for climbing," from stem of scandere "to climb" (see scan (v.)).
1550s, "person who examines critically," agent noun from scan (v.). From 1927 as a type of mechanical device, at first often in television technology, by mid-20c. used of radar and radiation imaging devices; later of computer digital readers.
1670s, "action of marking off of verse in metric feet," from Late Latin scansionem (nominative scansio) "a scanning," in classical Latin, "act of climbing," noun of action from past-participle stem of scandere "to climb" (see scan (v.)). There is a 1650s instance in English of the word in the literal sense of "action of climbing up."
1590s, "action of using ladders to scale the walls of a fortified place," from French escalade (16c.) "an assault with ladders on a fortification," from Italian scalata, fem. past participle of scalare "to climb by means of a ladder," from scala "ladder," related to Latin scandere "to climb" (see scan). For initial e-, see e-. Also in early use in English in Spanish form escalada, later corrupted to escalado. As the name of a brand of luxury SUV by Cadillac, from 1999.
1520s, "measured or prescribed size," altered (to conform to -ling words) from earlier scantlon, scantiloun, scantillon "dimension" (c. 1400), earlier a type of mason's rod for measuring thickness (c. 1300), a shortening of Old French escantillon (Modern French échantillon "sample pattern"), which is of uncertain origin; traditionally regarded as a deformed word ultimately from Latin scandere "to climb" (see scan (v.)). The sense has been influenced by scant (adj.). Meaning "small wooden beam" is by 1660s. Related: Scantlings.