What does Swear on my life mean?

Answer 1

To Swear on one's life is a verbal promise or oath made by the speaker, inteded to dispell doubt from the intended audience. It is effectively an offer to the recipients to take the life of the speaker if they are, in fact, lying, and so is taken to be an oath of truth and sincerity.

However, despite this, it is still used to mislead, as the "promise" is non-contractual: it does not actually permit the audience to justly take the life of the speaker if they transpire to be lying.