noun
body of water
Archaic term for a body of water, such as a lake or sea. Not used in modern Japanese.
古い文献では「積水」が湖や海を指すことがある。
In old documents, 積水 can refer to a lake or sea.
The exact derivation is uncertain; the kanji 積 (accumulate) and 水 (water) suggest 'accumulated water', i.e., a body of water.