Literature Reference: 谦谦君子，卑以自牧。——《周易·谦卦》 A modest gentleman cultivates himself with humility. Source from 'Zhouyi·Qian Gua'.
于: Thus, it is.
谦: Humble, modest, and gracious. Polite, with a deep understanding of etiquette.
Meaning: A modest and cultivated gentleman embodies the virtue of humility.