Where you go to have your Hebrew beliefs and philosophies freshened up and more-solidly established in your mind, after the decades of unavoidably associating with Gentiles has worn and numbed saidbasicvalues.
Doc Brown told Marty that he'd gone to a rejewvination clinic, but I am at a bit of a loss as to why he would feel any need to do that, since there was never any mention of his having Semitic/Hasidic ancestry or traditions.
When you fail at something in life (eg. failing an exam or not getting a job), go home and spend an hour just standing in the shower, propping yourself up against the wall with your eyes on your feet.
Caleb knew the only thing to do after he didnt get prefect was take a failure shower.