to save your life

to save your life

used in various expressions, especially can't (or couldn't ) do something to save your life , to indicate that the person in question is very incompetent at doing something.
The first recorded use of this expression is by Anthony Trollope in The Kellys and O'Kellys ( 1848 ): ‘If it was to save my life and theirs, I can't get up small talk for the rector and his curate’.
See also: life, save