Those who trace words back to Indo-European, frequently found
on this site, and not to insult any, but back even further to
the gibber-speak in the Lascaux caves, would probably find some
connection.

Well, gudgeon is tracked back (via Old French) to Late Latin gubia, but curmudgeon is of unknown origin (a bane to all would-be lexicographers). I very much doubt that whatever the humans, who painted the Lascaux caves, spoke that it can be recovered or even related to PIE.

Ceci n'est pas un seing.