Complex sentence: The Bayonet Constitution gets its derogatory name from its opponents, Kalākaua being forced to sign the constitution under threat of arms on July 6; rifles at the time were commonly fixed with bayonets.
Split into simpler sentences: The Bayonet Constitution gets its derogatory name from its opponents. Kalākaua had been forced to sign the constitution under threat of arms, and rifles at the time were commonly fixed with bayonets.