mountain well
Archaic expression for a well or spring located in the mountains. Not used in modern everyday speech; encountered in classical poetry or historical texts.
An old poem says, 'The water of the mountain well is cold and perfectly clear.'
Compound of 山 (yama, 'mountain') + の (no, possessive particle) + 井 (i, 'well'). The exact historical derivation is uncertain, but the term appears in classical Japanese literature.