...the modern (misleading) nickname that refers to the 1863 Remington contract rifle. And please, we've reached the point of discarding the shorthand "Zouave" for the 1863 Remington contract rifle.*
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* In fact the "Zouave" (not called that at the time) was merely the third iteration contract of the 1851 "Mississippi" two-band rifle pattern; the 1855 "Harpers Ferry" having been the second iteration. Yes Zouave units North and South had equipped with similar two-band pattern rifles (Southern versions included) but the 1863 didn't see much service, if any, during the war (there's some confusion about that since the type wasn't distinguished by contract iteration in the U.S. arsenal racks). Anyway not all iterations of this rifle pattern used the sabre bayonet of the kind you found; that was a contract specification.
The nickname "Zouave" was applied by repro makers back in the 1960s who based it on the use of similar 2-banders used by Zouaves on both sides during the war as seen in tintypes. Also, the actual surplused 1863s became popular for shooting competitions (good shooters) so the repro makers chose that type to reproduce to meet demand. "Zouave rifle" was a good selling name. We increasingly discard that shorthand anymore -- leave it to the gun dealers.