ballbreaker
noun
1
a difficult task, a boring situation; any circumstance that saps your spirit. The prosaic etymology leads to any task that strains the testicles; more likely that 'balls' represent power or spirit in this context US, 1942.
2
a powerful, assertive woman; someone who demands or actively exacts a difficult requirement. Taking 'balls' to mean 'power and spirit', this extends from the previous sense US, 1944