Archaic honorific term for one's own or someone else's mother. In modern Japanese, 母上 or お母様 are more common. Cross-referenced with ははうえ.
See also: 母上
In an old letter, it said 'Give my regards to your mother.'
A literary Sino-Japanese term for one’s mother, from the Chinese association of 萱草 with 北堂, the mother’s quarters in a household.