know somebody/something backwards
know something backwards
mainly BRITISH orknow something backwards and forwards
mainly AMERICANIf you know a subject backwards, you know a lot about it. I thoroughly enjoy lecturing and know my subject backwards. He will be very much in demand. He knows the business backwards. They know company personnel policy backwards and forwards.
know something backwards
be entirely familiar with something. 1991 William Trevor Reading Turgenev People who lived in the town knew it backwards.