Thing Not To Be Today: snarky.

 Snarky is such a brilliant word. It's not been around that long (1906, originally, but it faded away and then re-emerged in the very late 1900s. There was also a slightly older snarky (1866) which meant to snort).

The reason this word is brilliant is that it's so obvious what it means. The sn- beginning suggests it as a cousin in meaning to sneer and snipe and snarl; the -narky bit reminds us of the word nark meaning annoying or quarrelsome; and altogether there never was a word that suggested more plainly a cobbled together version of sarcastic and nasty.

There are sources online which confirm this sarcastic + nasty derivation, too.

Strictly speaking they're probably wrong, but hey...

Thing Not To Be Today: snarky. This word comes originally from snark, to find fault or to nag. There are similar words in Low German and Frisian. When the word re-emerged in 1997 it meant hostile, knowing and contemptuous. 

I suspect that this new snarky really is a combination of sarcastic and nasty/nark, and that this is an example of convergent evolution. But I can't imagine how anyone could prove it.

The creature in the Hunting of the Snark (Lewis Caroll, 1876) is entirely unconnected - unless it put the sound of the word into people's minds as an inspiration.

Anyway, let's not be snarky. Let's be kind, eh?