To save your life - Idioms by The Free Dictionary
to save your life
couldn't (do something) to save (one's) life
slang Cannot do something well or at all. Ugh, this art assignment is so annoying—I couldn't draw an apple to save my life. Rachel is so selfish! She couldn't consider another person's feelings to save her 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’.
References in classic literature
Take my advice, therefore, and if you wish to save your life
follow some other path.
In some states, the Highway Patrol road warriors have come up with some new tests to help provide you with instant, temporary free lodging behind bars - steel ones - to save your life
and the lives of innocent people who want nothing to do with a drunk driver.
There may be many others who have been injured or even killed by this problem but never reported it -- who would possibly imagine that the part in the car intended to save your life
-- might cost you your life?