According to the Yuan dynasty Zen master Zhongfeng Mingben ( 1263–1323), "gōng'àn" originated as an abbreviation of "gōngfǔ zhī àndú" (, Japanese "kōfu no antoku"—literally the "andu" "official correspondence; documents; files" of a "gongfu" "government post"), which referred to a "public record" or the "case records of a public law court" in Tang dynasty China. "Kōan/gong'an" thus serves as a metaphor for principles of reality beyond the private opinion of one person, and a teacher may test the student's ability to recognize and understand that principle.