Why do some people use $\ell$ to denote a prime number?

Question

Classically when I go to denote a prime number, I will use $p$ or $q$. However, I am learning a bit about Galois representations, and it seems that they like to use $\ell$ for a prime number, and I know that $\ell$ also tends to denote a prime number for things like $\ell$-adic cohomology. I was just a bit curious if there is some interesting historical reason that $\ell$ is chosen to be a prime in these cases, or if it is just because people think that $\ell$ looks pretty?