'water-containing' originates in English as a compound combining the noun 'water' (from Old English 'wæter') and the present participle form of the verb 'contain' (from Latin 'continere' via Old French), where 'water' meant 'water' and 'contain' meant 'to hold together.'

'water' comes from Old English 'wæter' and related Germanic forms; 'contain' derives from Latin 'continere' (con- 'together' + tenere 'to hold') and passed into English via Anglo-Norman/Old French. The compound form arose by directly combining the noun and participle in Modern English to describe something that holds or includes water.

Initially simply a literal combination meaning 'holding water,' the phrase has remained largely literal and is used descriptively in scientific and general contexts to indicate the presence of water.