From 《
庄子·
大宗师》 (Zhuangzi, Warring States):
泉涸,鱼相与处于陆,相呴以湿,相濡以沫,不如相忘于江湖 - 'when the spring dries up, fish stranded on land moisten each other with damp breath and spit; better had they forgotten each other in the rivers and lakes.' The original point was paradoxical - true freedom is not needing mutual rescue - but modern usage keeps only the tender half.