“空穴来风”的本义是？
What does 空穴来风 (“wind from an empty cave”) originally mean?
全球翻车率（内测预估）
A毫无根据
háo wú gēn jù · completely groundless
B凭空捏造
píng kōng niē zào · made up out of thin air
✓事出有因（有洞才有风进来）
shì chū yǒu yīn（yǒu dòng cái yǒu fēng jìn lái） · there's a reason behind it (no hole, no draught)
D山洞里很冷
shān dòng lǐ hěn lěng · it's cold inside the cave
有穴才来风——本义是“有根据”。现在人人用反，错的人多了，字典都投降了。
Originally: rumors have a source (wind needs an opening). Modern usage flipped it to mean “groundless” — so widely that dictionaries surrendered. Classic usage-drift trap.