Historical title used in the Meiji period government, equivalent to a vice-minister or undersecretary. Not used in modern government structures.
In the Meiji period, the dainagon was an important post as vice-minister of each ministry.
He served as vice-minister in the Meiji government.
He was appointed vice-minister of the Ministry of Public Works.
大輔 written the same way is read たいふ when referring to the older ritsuryō-system vice-minister title, versus だゆう for the Meiji-era one.
From the kanji 大 (great) and 輔 (assist), indicating a high-ranking assistant official. The reading だゆう is a historical Sino-Japanese reading.