"irritable, short-tempered," 1906, from snark (v.) "to find fault with, nag" (1882), literally "to snort" (1866), from an imitative source akin to Low German snarken, North Frisian snarke, Swedish snarka; and compare snarl (v.2), sneer (v.). Also compare narky "bad-tempered, sarcastic" (1895), British slang from earlier nark "annoying, quarrelsome, or unpleasant person" (1846), from nark (q.v.).
It seems to have emerged anew as a vogue word c. 1997 to indicate a "hostile, knowing, bitter tone of contempt." The back-formation snark (n.) "caustic, opinionated, and critical rhetoric" is by c. 2002 (compare snark (n.)). Related: Snarkily; snarkiness.