Barrington's 1873 song is interesting proof that a song *about* something (in this case the Peninsular War) may have been composed long after the event.

Since "Amerikay" isn't in Barrington's original, it probably edged its way in as more interesting and euphonious than "out of the way."

As for "firelocks" and "flasks of powder," there's no need to assume that Barrington was a military historian.

The song may have been composed (or rewritten as the case may be) as part of a long lost vaudeville skit of the 1870s.