rejewvination clinic

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 said basic values.

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.