Short form of
风马牛不相及 from 《
左传》: when Qi and Chu states are so far apart that even stray horses or cattle in heat (
风) wouldn't wander into each other's territory. Used on its own as in Lu Xun's
释迦牟尼，
可更与文艺界风马牛了 — 'Buddha has absolutely nothing to do with the literary scene.'
