旧城玖心旧你爹
[jiù chéng jiŭ xīn jiù nĭ diē]
In Chinese, the word for nine (九 'jiu') sounds like forever ('Jiu'), so '旧城玖心 (jiucheng jiuxin)' means 'old city and forever in my heart'. And '旧你爹' literally can be read as 'you father' but it could also means that deep in my heart I keep something old. Therefore, the whole nickname represents one's deep nostalgia and love towards a place that holds many memories, and some unbreakable relations, just like how people cherish fathers.