續一切經音義 6.155

6.155

谷響（上古屋反切韻山谷也又養也老子云谷神不死是為玄牝也又音欲下許兩反字林聲響也切韻響應也說文從音鄉聲）。

Valley echo (谷響: the first [character] is *gu*, fanqie 古屋. The Qieyun says: 'A mountain valley; also, to nourish.' Laozi says: 'The valley spirit does not die; this is called the mysterious female.' It is also pronounced *yu*. The second [character] is *xiang*, fanqie 許兩. The Zilin says: 'Sound and echo.' The Qieyun says: 'Resonant response.' The Shuowen jiezi says it is derived from the sound radical 音 with 鄉 as phonetic).