TITLE: Why are they called L-functions?
QUESTION [12 upvotes]: I was hoping to see this pop up on the recent big list question about etymology or terms and symbols. Since it has not, and I can't find an answer, I will ask:
What is the reason for the $L$ in $L$-function? I've read that the general use of the term cames from Dirichlet's $L$-functions $L(s,\chi).$ Was there any motivation behind Dirichlet's use or was it just an arbitary choice?
If so, is there any compelling reason that we keep this name other than tradition?

REPLY [4 votes]: Whatever the historical reasons are, I think it is a good thing to use the terminology 'L-function' because of Langlands's amazing contribution to the theory of automorphic forms.
Moreover Langlands functorialities are stated in terms of the 'L-group'.