I have known what a pier-six is and used it plenty since I was first introduced to boxing. I often heard Don Dunphy in particular say: "It's a real pier-sixer, " or pier-six, or pier-six brawl. Some form of pier-six. I know that we are referring to a brawl when we say pier six, but what does the pier six refer to? @KasimirKid? I just love asking you these questions.
A few quick searches did hinted at the origin but didn’t specify an exact first use but basically: Waterfronts where longshoremen worked (loading and unloading ships) were known as rough places with rough people (tough lives, tough work, lower wrung on the economic ladder) and rougher bars. And piers were numbered, just as runways are — a ship would have a certain pier as its destination and whomever owned or was contracted to transport the contents from this ship or that would have a crew of stevedores there to unload it when it arrived. So a fight on the waterfront or in a waterfront bar was going to be more violent because you had very physical men with little mercy or sympathy in them. Pier six, per one reference I saw, may have been that specific pier being one of the more notorious for violence in Staten Island, but there was no citation for how they arrived at that particular pier six.
The Staten Island reference I've also heard, however what I read was that fights (possibly unsanctioned?) were held there. No idea...this is a reference probably 100 years old, so maybe nobody knows the true origin.
Its origins are rooted in the time Boston Tom McMustache had a shootout with Sailor Goldstein on Pier 6.
To clarify, that was Barbados Boston Tom McMustache, the one from New Mexico by way of Minnesota — not to be confused with Philadelphia Boston Tom McMustache, who was born on the Baja peninsula and raised in Vancouver before settling in Barbados. Barbados Boston Tom was fishing on pier six when Sailor Goldsyein kicked his bait into the water to precipitate the incident.