I have been using the notation $\wp^{-1}(a)$ for a root of $T^p-T-a$ (in characteristic $p$), which I borrowed from Bourbaki, but I have also used $\wp_2^{-1}(a)$ and $\wp_3^{-1}(a)$ if the characteristic had to be mentioned explicitly.
This morning I came across an original notation for $\wp_p^{-1}(a)$ in a paper by Davenport and Hasse in the Journal für die reine und angewandte Mathematik, 172 (1935). I cannot display it here because Knuth was not aware of it when he created TeX, so all I can do is to provide a link to their article. The notation appears on the last line of the first page (p.151) and it is defined in the first line of the second page (p.152).
Clearly, the reason behind their notation is its similarity to $\root p\of{}$. It is a less angular and more curvaceous version of the radical, with the loop closing upon itself.
I wish the people responsible for TeX and Unicode will give a second life to this little gem.

