Origin and history of scan

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," from PIE *skand- "to spring, leap, climb" (see scale (v.1)).

The notion in the Late Latin image is unclear; one suggestion is that it is of tapping the feet in time with the verse or the rising and falling rhythm of poetry.

The sense of "look at point by point, examine minutely" (as one does when counting metrical feet in poetry) is recorded by 1540s, and is from the poetic sense rather than the source of it.

English lost the classical -d- probably by confusion with suffix -ed (compare lawn (n.1)). The intransitive meaning "follow or agree with the rules of meter" is by 1857.

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.