I'm Telling!

My output for this blog would not be significantly diminished if I just called it "Slate Fuck-Up of the Day".

Here's a sentence from one of Slate's two(!) advice columns:

It's Lisa and Tim who are your old friends here and therefore command your loyalty—not Vincent and Laura (the potential victims)—so I'd leave the tattle-tailing to someone else.

Now, the word "tattle-tale" (or, if you like, "tattletale") means someone who tattles on another by telling tales. Couldn't be more obvious. If you are determined to turn it into a gerund, which is probably not a good idea, then it would be "tattle-taling". Emphatically not "tattle-tailing".