Definitely a meta tag. I'd expect tags in somewhat similar spirit to be created and removed in the past - but a quick search lead me only to the tag
joke which was created and removed on meta.
math.meta.stackexchange.com/posts/18906/revisions math.meta.stackexchange.com/revisions/18906/1 
Show that $f(x) \to 0$
without using any methods.
Thank you.
