It seems there was a Musty Ale Stores in Liverpool, England in the second half of the 1800s. See these references, to which however I don’t have the full access. Even from the summaries though it is clear such a place existed in Williams-street, held by different tenants over time including a James O’Connor.
The first story seems to recount judicial proceedings in which a justice, Sir James Hannen, questions the oddity of the name Musty Ale Stores, only to be told it denotes some old type of Welsh ale! While the term, ale stores, would suggest a place to stock ale, the Musty Ale Stores appears to have been a public house or a victualler of some kind.
I won’t go into Welsh ale of yore except to note some used honey, the famed braggot, and some was spiced. This gets more curious by the minute. Might American musty have been spiced, possibly? I can’t rule it out, but I’d incline against and will stand by my theory in the last post, which gains support from bartender Tim Daly’s suggestion in 1903 to blend lager and old ale to make a musty. Bartenders have lots of bitters and spices at their disposal, or an expert like Daly would have, so it would have been easy for him to suggest spices for his musty; he didn’t.
Given the long literary use of the term musty ale, it is not a surprise some people used the term concurrently, I mean in real commerce. Whether the usage was anything more than regional, isolated, erratic, or whimsical I can’t say.
It’s in a Philip Massinger play, A New Way To Pay Old Debts, but once again that doesn’t mean the term was in daily commerce everywhere, and many years of reading technical and popular historical literature on British beer and brewing has never produced an example (until now).
Still, the Liverpool example seems quite real. Maybe the term was used just there and, being a port, a Scouser found his way to America. Maybe.