Complex sentence: The doctrine of exoneration of liens (sometimes simply referred to as "doctrine of exoneration") refers to a common law rule that property given through a will has its encumbrances (i.e. mortgage) paid by the originating estate, not from the property itself.
Split into simpler sentences: The doctrine of exoneration of liens (sometimes simply referred to as "doctrine of exoneration") refers to a common law rule. The rule says that encumbrances (i.e. mortgage) of a property that is conveyed by a will is discharged with funds from the originating estate, not from the property itself.