English language is a dynamic, changing thing. Some terminology just becomes ratified by use. For example, the M1866 Winchester wasn't called that until the Model 1873 was introduced. Prior to that what we call a '66 was simply the "Improved Henry".
Did you know there is no such thing as an "Artillery Colt Single Action Army"? That is a collectors' term for the cut-down SAA's with 5-1/2" barrels. Neither, originally, was there such a thing as a Colt' Single Action revolver in .44 WCF. Nope, it was "The Colt's Frontier Six Shooter."
Strictly speaking, what we call the Remington M1858 is really the New Model Army revolver. The reason for the '58 appellation is that is the patent date stamped on the gun. Et cetera, et cetera!
Kinda like the patent "tonic" back in the 1940's, "Hadacol". It was supposed to make older folks feel better. Of
course it made them feel better...it was 90 percent alcohol, and they were half-bombed all the time!
(FDA finally made them take it off the market.) Why did they name it "Hadacol"? Well, they Had-a-call it somethin'!