Borrachuelo means drunkard. It refers to the amount of rum and brandy-flavoured jarabe (syrup) this chocolate sponge soaks up. This is a good recipe for sponge, as it is lightened by egg whites and leavened by yeast, which also gives it a nutty richness.
When making the sponge, make sure the equipment is really clean because any fat or oil will stop the egg whites from fluffing up. The other little tip is to always think light when making a sponge — a gentle touch will