In Python (and every other programming language) you can have a function with more characters long name. For example, print('x').
I have wondered, if this is possible in math, too. I have found that you can have a function with Latin name (somewhere I have found that group homomorphism can be marked with big phi, so even Greek letters are included). You can also add bars at the names ($f´(x)$). You can add indexes ($f_1(x)$). (Small question: Can be functions named in Hebrew alphabet?)
Main question: Can be functions named with more characters (for example, $ab(x)$)?
Notation for trigonometric functions uses multiple letters, with especially many if they are inverse, get a c at the end (e.g. $\operatorname{tanc}x$), hyperbolic or non-standard, e.g. the haversine. (The idea of a function named $\operatorname{archaversinch}x$ is amusing.)
Other examples include $\exp$, $\ln$ and $\operatorname{erf}$. Then you get special functions such as Airy functions, Clausen functions, the cosine, exponential and sine integrals, Hermite polynomials, and so on. Pretty much every function named here is suitable.
Note, however, that multiple-letter names are typically deitalicised, e.g.
\expis equivalent to\operatorname{exp}.