I was reading a wikipedia article about the evolution of global financial system: https://en.wikipedia.org/wiki/Global_financial_system#Interwar_period:_1915%E2%80%931944.
In the passage about the pre-WWI financial system, it is written that
[Immediately before the outbreak of WWI,] European tensions and increasing political uncertainty motivated investors to chase liquidity, prompting commercial banks to borrow heavily from London's discount market. As the money market tightened, discount lenders began rediscounting their reserves at the Bank of England rather than discounting new pounds sterling.
What do "rediscounting reserves" and "discounting new pounds sterling" mean?