Literature Reference: 秦川雄帝宅，函谷壮皇居。——《帝京篇十首》 The Qinchuan region is a majestic imperial residence, and the Hangu Pass strengthens the royal abode. Source from 'Ten Poems of the Imperial Capital'.
函: The term refers to a letter and its envelope.
谷: Surname, the essence of sustenance.
Meaning: Hangu refers to the Hangu Pass, symbolizing strength and grandeur, representing power and protection.