White是“白色”，knuckle是“指关节”。White-knuckle字面解释是“指关节发白的”，这是什么意思呢？请看对话：

    A: The weather report says there will be a heavy storm coming our way this week.

    B: Then, you should take extra care while driving. The storm will blur your vision, making for a white-knuckle commute from home to the office.

    Note: Driving in a heavy storm is dangerous. You’ll probably find yourself holding onto the steering wheel so fast that the knuckles of your hands will turn bloodless and appear white in color. You can observe that people’s knuckles turn white in complexion when they clench their fist. “White-knuckle” means “causing or experiencing fear or anxiety,” similar to the Chinese saying “causing sweaty palms.”