你是我的第一夫人你是我的不二先森
[nĭ shì wŏ de dì yī fū rén nĭ shì wŏ de bù èr xiān sēn]
This nickname conveys a deep commitment in a relationship, suggesting that the person is irreplaceable and unique. '第一夫人' literally means 'First Lady,' symbolizing respect and prominence, while '不二先森' suggests the person is unparalleled (the phrase uses homophonic play to mean both 'number two does not exist' and includes a pun using a common way to refer to someone affectionately as 'Xian Sen').