snapdragon n.

1550s, perhaps late 15c., "a quick, sudden bite or cut; an eager seizing," from snap (v.), or, if the earlier date, a noun from Dutch or Low German snappen "to snap," which are probably related to Middle Low German or Middle Dutch snavel "bill, beak," which Watkins traced to a hypothetical Germanic root *snu- forming words having to do with the nose, imitative of a sudden drawing of breath (see snout).

The sense of "quick movement" is recorded by 1630s; that of "something easily done" is 1877. The meaning "crispness, pithiness" is from 1865, American English (Scottish English had it by 1790 in an adjectival sense of "sharp, smart"). The meaning "brief or sudden spell" of weather (usually cold) is from 1740. The meaning "catch or fastener (of a purse, etc.) 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 photographic snap-shot" is from 1894. U.S. football sense is from 1912, earlier it was snap-back (1880), which also was the name for the offensive center position. Slang snaps "handcuffs" is by 1895. Snap, Crackle and Pop, cartoon characters associated with Kellogg breakfast cereal Rice Krispies, are from 1940.

As an adjective (1790) commonly used to indicate instantaneous action, as in snap judgment (1841).

mid-13c., dragoun, a fabulous animal common to the conceptions of many races and peoples, from Old French dragon and directly from Latin draconem (nominative draco) "huge serpent, dragon," from Greek drakon (genitive drakontos) "serpent, giant seafish," apparently from drak-, strong aorist stem of derkesthai "to see clearly," from PIE *derk- "to see" (source also of Sanskrit darsata- "visible;" Old Irish adcondarc "I have seen;" Gothic gatarhjan "characterize;" Old English torht, Old High German zoraht "light, clear;" Albanian dritë "light").

Perhaps the literal sense is "the one with the (deadly) glance." The young are dragonets (c. 1300). Fem. form dragoness is attested from 1630s. Obsolete drake (n.2) "dragon" is an older borrowing of the same word, and a later form in another sense is dragoon. Used in the Bible generally for creatures of great size and fierceness; it translates Hebrew tannin "a great sea-monster," and tan, a desert mammal now believed to be the jackal.