What is really meant is that there is a shortage of assets in relation to liabilities.
In the modern system assets and liabilities always balance. That doesn't mean there can't be an abundance or shortage of money. It all depends upon how much new money is being injected into the system and whether resources are being under-utilised meaning there is idle capacity in the economy or whether they are in short supply creating more demand than there is productive capacity.
I don't know much about pre-fiat systems but they were certainly revenue constrained, unlike modern governments.