Hello, I think there is a typo of l3names.dtx.
Index: l3kernel/l3names.dtx
===================================================================
--- l3kernel/l3names.dtx (revision 3691)
+++ l3kernel/l3names.dtx (working copy)
@@ -612,7 +612,7 @@
\tex_let:D \tex_everymath:D \frozen@everymath
\tex_let:D \tex_hyphen:D \@@hyph
\tex_let:D \tex_input:D \@@input
-\tex_let:D \tex_italic_correction:D \@@italiccorr
+\tex_let:D \tex_italiccor:D \@@italiccorr
\tex_let:D \tex_underline:D \@@underline
% \end{macrocode}
% That is also true for the \pkg{luatex} package for \LaTeXe{}.
regards