湯 Soup or Hot Water?
In Chinese-speaking communities, 湯 means 'soup'. In Japanese, however, its meaning is 'hot water'. As a matter of fact, it finds its origin in Classical Chinese.
It is clearly defined in Key to Chinese Characters (Shuowen jiezi 說文解字), the 2nd century Chinese dictionary that 湯 means 'hot water' (熱水也; see vol. 11a). Therefore, the Chinese idiom 赴湯蹈火 is literally 'to get into hot water and tread on the fire'.