It's the ides of April, so why don't we call it that?
I like the idea of a term for the middle of the month. We have the first of the month and the last of the month. So "the ides" is a good marker, letting us know we're halfway through. No one says it, though.
There are lots of words from the past that we've thrown away, words that are still good, like those rollover minutes on TV. Varlet. Whippersnapper. Mewl. Strumpet. I could go on.