Brewer's: Last Man
(The) Charles I. was so called by the Parliamentarians, meaning that he would be the last king of Great Britain. His son, Charles II., was called The Son of the Last Man.
A weirdly grotesque poem by Thomas Hood.
So there he hung, and there I stood, The last man left alive.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894