Backfired: to fail unexpectedly; to fail with an undesired result.
Not a noun, but a verb. A similar word is to have an action boomerang: to recoil or return unexpectedly, causing harm to its originator; backfire.
Shooting oneself in the foot is erroneously thought to have shifted meaning from the intentional act in WWI of soldiers to escape battle (a somewhat befeficial outcome) to the now popular meaning of to do or say something stupid which causes problems for you. (TFD) However, this appears to be a misconception.
An early example can be found in
a sad report in the Appleton Crescent newspaper of August 1857: “Mr. Darriel S. Leo, Consul to Basle, accidentally shot himself through the foot, four or five days ago, in a pistol gallery at Washington, and died on Sunday of lockjaw.” (WorldWideWords)
The author concludes
I’m sure the expression shoot oneself in the foot derives from such accidents, usually the result of incompetence, and has led to our current meaning of making an embarrassing error of judgement or inadvertently making one’s own situation worse. That men did it deliberately as a way to avoid combat is only a side meaning.