Then he'd pulled his Hebraic letter fantasies in "La muerte y la brujula," something about the Tetragrammaton, JHVH, God's unpronounceable Hebrew four-letter name, and the serial murders of Jews.
This second term is Borges's Tetragrammaton, sometimes rendered, JHVH, as he does in "La muerte y la brujula" (OC 507).