TITLE: Origin of the Socle of a module
QUESTION [10 upvotes]: Where does the notation $\mbox{Soc}(M)$ (the sum of all simple submodules of a module $M$) first appear?

REPLY [3 votes]: Just to establish some more reference points:
In the book
[Curtis, Charles W.; Reiner, Irving. Representation theory of finite groups and associative algebras. Pure and Applied Mathematics, Vol. XI Interscience Publishers, a division of John Wiley & Sons, New York-London 1962],
the socle of a module is defined, but no special notation is used.
In the paper
[Curtis, C. W.; Jans, J. P. On algebras with a finite number of indecomposable modules. Trans. Amer. Math. Soc. 114 1965 122--132.],
the notation $S(M)$ is used.
In the book
[Anderson, Frank W.; Fuller, Kent R. Rings and categories of modules. Graduate Texts in Mathematics, Vol. 13. Springer-Verlag, New York-Heidelberg, 1974],
the notation ${Soc} \; M$ is used.