Comprehensive resource for understanding and mastering English idioms
The idiom "bang head against wall" means to hit one's head repeatedly against a wall or any hard surface in frustration, anger or desperation. It can also mean to encounter an obstacle or situation that is difficult to overcome or solve. The figurative meaning suggests that someone is trying very hard but is not making progress and is becoming increasingly frustrated.
The origin of this idiom is not entirely clear, but there are several theories. One theory suggests that it comes from the medieval practice of trying to break one's own skull in order to prove oneself as a warrior or soldier. Another theory suggests that it comes from the old method of punishing people by making them stand with their backs against a wall until they passed out. The idiom may have also originated from hitting one's head on a wall or other hard surface out of anger, frustration, or desperation.