南海以南思念未归北海以北深海未眠
[nán hăi yĭ nán sī niàn wèi guī bĕi hăi yĭ bĕi shēn hăi wèi mián]
With deep poetic tones, this nickname refers to places far south ('South Sea' region where feelings are not reciprocated/unresolved) and areas extremely north ('North Sea') that suggest unpeaceful thoughts like sleeplessness. A longing or melancholic mood towards someone is implied by this distance.