I'm reading a 1975 paper by a Polish mathematician (Michal Misiurewicz) written in English and published in Astérisque. It uses some notation that I'm not familiar with, although I can understand it from the context. It seems he's using the notation $E(x)$ to represent the floor function, $\lfloor x\rfloor$. Is this usage well known? (it occurs to me that E is the first letter of entier, the French word for integer).
Although I have never seen such usage of this notation it is worth noting the following quote from the Wikipedia page on this topic:
"The notion of the integral part or integer part of $x$ was first introduced by Adrien-Marie Legendre under the name entier (French for "integer") in 1798, when he needed the concept for his proof of the Legendre's formula."
Thus it would make sense to shorten such an "entier" function to simply $E(x)$.
Edit: In some European countries the modern name for the floor function is the "entier" function (see this Dutch Wikipedia article). This may be the case in Poland.