E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A wine sold for port, but of quite a different family. As a widow retains her husbands name after her husband is taken away, so this mixture of potato spirit and some inferior wine retains the name of port, though every drop of port is taken from it.
We have all heard of widows port, and of the instinctive dread all persons who have any respect for their health have for it.The Times.