The Bábí movement developed out of a school of Twelver Shiism known as Shaykhism, Mírzá Husayn 'Alí took as his Bábí title the divine name Bahá' (Splendor).

The Bábí movement developed out of a school of Twelver Shiism known as Shaykhism, so called after its founder Shaykh Ahmad al-Ahsá'í (d. 1826), which contained millenarian emphases. Many prominent Bábís were converts from Shaykhism which came under the leadership of Sayyid Kázim Rashtí, al-Ahsá'í's successor….

Mírzá Husayn 'Alí quickly became a prominent figure in the Bábí movement, and increasingly played a low-key leadership role after the government's incarceration of the Báb in Azerbaijan in 1847. When the Báb declared himself the Qá'im, the messianic return of the Twelth Imám, Bahá'u'lláh organized a conference of Bábí leaders in the hamlet of Badasht to publicize this claim and obtain a consensus about it. There, the Bábí disciple and poetess, Țáhirah Qurratu'l-'Ayn, scandalized some of the faithful by casting aside her veil to symbolize the advent of a new dispensation. At this conference, Mírzá Husayn 'Alí took as his Bábí title the divine name Bahá' (Splendor). In the late 1840s, fighting broke out between Bábís and Shí'ís in Mazandaran, Zanján and Nayríz. Bahá'u'lláh was not present when government troops besieged the shrine of Shaykh Ṭabarsí in Mazandaran, where hundreds of Bábís had gathered, because Shí'í adversaries imprisoned him in the town of Amul. They at length released him, but they stripped him of at least some of his property.

(From Iran East and West, edited by Juan Ricardo Cole, Moojan Momen)

https://books.google.com/books?id=7xbzoJ5wFG4C&pg=PA3&lpg=PA3