Yes, the eggs of hair lice continue to develop and thrive behind the ears of countless children and their poor parents, but the cry of you nit! has, by and large, ceased to sound through the corridors of...well, anywhere, really.
We still have nit the unit of radiance (equivalent to one candela per square metre, which must be quite dim), and nit the unit of information equal to 1.44 bits (which isn't a lot, either).
If you're in Australia then to nit is to keep watch while your mates do something that's probably illegal,
But the commonest sort of nit of my British childhood, what I might describe as the you nit! unit has fallen out of use. This unit describes someone about as dim as the nit unit of radiance, and about as lacking in useful information as the nit unit of information.
This nit is short for nitwit.
A nitwit is a bad thing to have around, but there's something even worse, and that's a witch nit.
What nits? you will say, which is fair enough because they are very rare. In fact you only find witch nits in one book, and that was only published yesterday. It's called CLASS SIX AND THE NITS OF DOOM, and it's by...oh, someone or other.
One small warning: it's impossible to read without scratching.
Word To Use Today: nit. The louse sort of nit comes from the Old English hnitu; the unit of light comes from the Latin nitor, brightness; the unit of information comes from N(aperian dig)it; and the Australian look-out comes from nix, from the German nichts, nothing.