你走后情书写给山鬼
[nĭ zŏu hòu qíng shū xiĕ jĭ shān guĭ]
'Nǐ zǒu hòu qíngshū xiě gěi shānguǐ' roughly translated as 'love letters written for mountain ghost after you leave'. 'Shānguǐ' comes from Chinese mythology. It often describes a spirit living in the mountains. So, this nickname suggests an elusive love or longing.