Wu Collection, Lower Volume
Radical: Cave (xué)
Character: 穸
Kangxi stroke count: 8
Page 862, Entry 28
Guangyun (Expanded Rhymes), Jiyun (Combined Rhymes), Yunhui (Collection of Rhymes), Zhengyun (Correct Rhymes): Pronounced xi. The dark chamber of a grave.
Shuowen (Explaining Graphs and Analyzing Characters): Refers to the burial process (zhunxi).
Zuo Zhuan (Commentary of Zuo): In the thirteenth year of Duke Xiang, the Viscount of Chu told his ministers: This is about the burial affairs of the Spring and Autumn period.
Commentary: Zhun means thick; xi means night. It refers to the deep darkness within the grave, like a long night.
Another definition states that a long burial is called zhun, and a long night is called xi.
Also, Zihui Bu (Supplement to the Collection of Characters) uses it as a loan character for the word meaning to investigate (jiu).
Han Dynasty, Fan Min: Perusing the path of study, there is no text unseen.
Also rhyming with the pronunciation yue:
Zuo Gui, Yang Hou Lei (Dirge for Empress Yang): Wings joined in the white house, flying together in the purple pavilion. Mourning the empress, grieving for the empress, early to face the burial.