And of course the title is an alt phrasing of the line that gets translated as Cloud Recesses in Mó Dào Zǔ Shī ☺️
云深不知处, Yúnshēn Bùzhīchù — derived from Jia Dao’s “Visiting the Absent Hermit”:
松下问童子，言师采药去, 只在此山中，云深不知处
(When I questioned your pupil under a pine tree, he answered, “My teacher went to get herbs.” But how can I tell toward which corner of the mountain, through all these clouds?)
Which literally translates in English to “somewhere unknown deep in the clouds,” or of course, “cloud-hidden, whereabouts unknown.”