海底月捞不起心上人不可及
[hăi dĭ yuè lāo bù qĭ xīn shàng rén bù kĕ jí]
Translated as 'Can’t catch the moon from the ocean bottom, nor the unattainable lover in my heart.' The person who picks this nickname probably feels wistful and longing but is unable to attain what they wish for.