天行 "the revolution of nature's cycle" (as in《周易》天行健 and《荀子.天論》天行有常):
天: "the heavenly bodies (e.g., stars, planets), the universe, nature"
行 xing2 (a verbal noun): revolution, a recurrent or rhythmical pattern of development (反復循環的發展,e.g., 蛇行:左扭右扭, 左扭右扭...;人行: 左腳右腳,左腳右腳...; 獸行:前腳後腳,前腳後腳...; 車行:輪子轉來轉去,轉來轉去...; ebb and flow)
Connotations of 天行: (1) ever-evolving development (that is, 健 in 天行健), (2) inevitable fate (that is, 常 in 天行有常; 必然之事, e.g., 天下大勢分久必合,合久必分)
《天行九歌》歌詞: 「看流沙聚散...君不見青山, 豪杰冢化塵煙, 豪杰冢皆化塵煙。」==> inevitable fate (聚了又散, 沒有不散的筵席...豪傑終究會死,皆化塵煙).