In the light of this, 白月光 doesn't just mean 'light of his life'.

白月光 actually means "something that is deeply yearned, but unreachable". It also means a perfect lover that one cherishes deeply, but is beyond their reach. https://twitter.com/RequimOfGlory/status/1265052773227388929

The term was first created in a novel called "Red Rose, White Rose" by Eileen Chang but was popularised from the classic historical drama "The Story of Yanxi Palace". Both term refer to someone that is deeply engraved in one's heart and mind, but they can never have them.

Oh wait, I messed up. In "Red Rose, White Rose", it tells a story of a self-made successful man (Zhenbao) who had goals in his life and an "ideal world/future". He envisioned how his perfect wife would be that will fit in with the society's standards.

But one day he fell in love with a married woman (Jiaorui), and the two started an affair. It was thrilling and full of passion, until the woman asked her husband for divorce so she could be with him. He was ashamed of what the society and his family would think him,

so he left her afterwards and married the perfect wife (Yanli) even though he didn't love her at all. Then there's a quote, "Maybe every man had two such women. Marry a red rose and eventually she'll be a mosquito-blood streak smeared on the wall,

while the white one is 'moonlight in front of my bed'. Marry a white rose and before long she'll be a grain of sticky rice that's gotten stuck to your clothes; the red one, by then, is a scarlet beauty mark just over your heart."

Basically, it means that if Zhenbao chose to marry Jiaorui (Red Rose), his ideal/perfect future and wife would be unreachable like the white moonlight (明/白月光). While if he marries Yanli (White Rose), the burning passion will stay at his heart.

All in all, marrying both roses will have bad outcomes for himself either emotionally or his status. But during this time, the phrase is not widely known yet. It became popular after the drama "Story of Yanxi Palace". Empress Xiaoxianchun was first empress of Qianlong Emperor.

She was known as a virtuous woman who is selfless and looked after Emperor Qianlong and the people in the palace well, she was a very respected empress. She was also favoured and loved deeply by Qianlong Emperor. One day she fell gravely ill and passed away.

But after her passing, Qianlong emperor would often visit her grave with wistful longing and remained heartbroken until the end of his life. Fans described her as his "白月光". Always longing, but never reaching.

So 白月光 actually has several different meanings. Even tho the term was not very intimate in Eileen Chang's novel. The term is more well known as a lasting deep yearning of something that we can never have. An unreachable longing.