Originates in 《
汉书·
霍光传》:
诸事皆先关白光，
然后奏御天子 - all matters were first reported (
关白) to the regent Huo Guang before reaching the emperor. Japan later borrowed the term as
関白 (Kanpaku), the chief regent title held by Toyotomi Hideyoshi and others - that's the meaning most learners encounter today.
