It feels to me, without any external substantiation and without knowing anything about shibboleth, that "insult to father's stones" might refer to an error raised by calling code or a parent process, in protest of a condition caused by called code or a child process. Stones could be an overly literal translation of "steps." So something about the child process "insulting" the execution (steps) of the parent?

Oh and someone downvoted that. I love this site and all you wonderful people.