late 15c., "quick, sudden bite or cut," from Dutch or Low German snappen "to snap," probably related to Middle Low German or Middle Dutch snavel "bill, beak," from West Germanic *snu-, an imitative root forming words having to do with the nose (see snout).
As an adjective from 1790. Commonly used to indicate instantaneous action, e.g. snap judgment (1841). Sense of "quick movement" is first recorded 1630s; that of "something easily done" is 1877. Meaning "brief or sudden spell" of weather (usually cold) is from 1740. Meaning "catch or fastener that closes with a snapping sound" is from 1815. The card game name is attested from 1881, from a call used in the game. Meaning "a snap-shot" is from 1894. U.S. football sense is from 1912, earlier snap-back (1880), which also was a name for the center position. Snap, Crackle and Pop, cartoon characters associated with Kellogg breakfast cereal Rice Krispies, are from 1940.
1520s, of animals, "to make a quick bite," from snap (n.). Meaning "to break suddenly or sharply" is first recorded c.1600; the mental sense is from 1970s. Meaning "come into place with a snap" is from 1793. Meaning "take a photograph" is from 1890. U.S. football sense first recorded 1887. Related: Snapped; snapping. To snap the fingers is from 1670s. Phrase snap out of it recorded by 1907. Snapping turtle is attested from 1784. Snap-brim (adj.) in reference to a type of hat is from 1928.
A short sharp sound; a click. Used especially of cardiac sounds.
To become sharply attentive and responsive: His soldiers snapped to and did what they were told
[1940s+; fr the quick way a military person snaps to attention on command]
[the third noun sense is found by 1648, but the current street and sports use is probably not a survival; the third verb sense is fr the cliche´ ''something snapped in his mind'']