The Vietnamese word "phân bắc" translates to "night-soil" in English. It refers to human waste, particularly the feces that are collected at night for use as fertilizer in agriculture.
In a more advanced context, "phân bắc" can also refer to the practice of composting human waste, which is part of sustainable agriculture.
While "phân bắc" specifically refers to human waste, it can also be used metaphorically in literature or discussions to signify something unwanted or unpleasant.