Green’s Dictionary of Slang

answer the last muster (roll) v.

to die.

1870		Belfast Morn. News 13 July 4/1: My Jane is waiting for me when I die! [...] at the last muster-roll.
1906		Aberdeen Jrnl 26 Mar. 4/7: Sergeant-Major Wilson [was] able to congratulate them on having passed another year without any of therm having to answer the last muster roll.
1936		L. Pound ‘American Euphemisms for Dying’ in AS XI:3 199: Answered the last muster.