> That looks like a good start!  Though, I can't find the string @elt in
> the output of
>
> \documentclass{article}
> \usepackage[german]{babel}
> \begin{document}
> \makeatletter
> \message{\bbl@languages}
> \makeatother
> \end{document}

Replace

\message{\bbl@languages}

by

\show\bbl@languages

to see the actual (unexpanded) contents of \[log in to unmask] Or to see it
in action, try

\documentclass{article}
\usepackage[german]{babel}
\begin{document}
\makeatletter
\def\bbl@elt#1#2#3#4{// #1 - #2 - #3 - #4}
\message{\bbl@languages}
\makeatother
\end{document}

Javier