eternal well; well that never runs dry
Archaic term for a well with a perpetual water supply. Not used in modern Japanese outside historical or literary contexts.
In old documents, the word 生井 is used to refer to a well that never runs dry.
Compound of 生 (iku, 'living, alive') and 井 (i, 'well'). The exact historical derivation is uncertain, but the kanji suggest a well that is 'alive' with water.