Earlier than 1847, Irosin was a far inland valley unspoiled by human settlers and covered by vast forest expanse teeming with wild animals. Irosin was among the last places in the Philippines to be populated. Most of the natives during the early 1800s lived along the coastal areas where it was more accessible to commercial, travel and communication activities at the time.

The place had been an undisturbed sanctuary for wildlife until settlers from Bulusan came in search of wild quarry and rattan. These pioneers, using the slash-and-burn method, cleared a settlement beside a river which gave birth to a clearing called Hin-ay, an Albayanon word which denotes the arrangement of the abaca yarn or tupos into a zigzagging pattern ( hinan-ay ) in preparation for its actual weaving. Accordingly, the hin-ay or the pattern was the image drawn to connote the waving rivers crisscrossing from the mountains down the valley. In yet another account, the word hin-ay was purported to have been derived from the term an-hay which means gradually ascending. The original settlement which is now called San Agustin is located east of the town proper at a higher elevation, thus the gradual ascent from the lower villages to the then barrio center of San Agustin.

It was in 1847 when Hin-ay was declared a barrio of Bulusan. The Gobernadorcillo of Bulusan visited Hin-ay and appointed Apolonio Capido as the first barrio lieutenant. Deeply influenced by Catholicism brought by the Spanish friars, the natives of Hin-ay constructed a makeshift chapel and dedicated it to their patron Saint Michael Archangel. As years passed, the original clearing has grown into a bustling community and eventually the settlers requested the church authorities to bestow upon San Miguel a status independent and separate from that of Bulusan. The petition was granted and Holy Masses on Sundays and holidays of obligations were held regularly. In 1876, the Parish of San Miguel was officially recognized with Father Mariano Miranda as its parish priest and consequently, the name Hin-ay was changed to San Miguel. On December 12, 1879, through a Royal Decree executed by the Governor General Domingo Moriones y Murillo, San Miguel became a duly constituted pueblo or town.

During those years Pedro Fruto (1881-1882), Domingo Gamba (1883-1884) and Juan Gallarda (1885-1886) were the public officials who were addressed as Capitanes del Pueblo . From the year 1880, the town of San Miguel flourished as an independent political unit under the Province of Albay when Sorsogon, until October 10, 1894, was not yet separated from its mother province. The first Guardia Civil came to Irosin in 1883. Its members were Filipinos headed by a Spanish Captain. With the spread of the underground movement called by the Spaniards hombres rebeldes in 1894, more Spanish forces called casadores had been dispatched to Irosin. They imposed curfew hours in a bid to curtail the local uprisings.

It was during the incumbency of Father Esteban Rivera in 1887 when the name San Miguel was again changed to Irosin. The word was derived from the local term iros which means to cut-off a part. The word was traced to have come from an old tailor’s term synonymous with tabas as in ” irosi an hiniro ” or cut a part of the cloth. Iros was the image most probably drawn to connote the gush or flow of floodwaters eroding riverbanks and cutting through lands to eventually form another river or river route.

The old historical tale of Elias Cuadro and Sabiniano Gacias (1937) runs thus:

“Gnaning maontoc na an guibong pagtabas,
pag-iros can salog, sa banua pagrompag;
segun supersticion, encantong balignag,
maraot na pagtubod, ay sosogon nangad.”

“Con caya guinibo, iboniag Irosin,
gnaranan an banua, apodon nin siring;
ta sogno-sognoon an hoyog na quiling,
pag-iros can tubig nin banuang Irosin.”*

Giving credence to the above account, Irosin was indeed frequently eroded due to inundations of the rivers. On the 24th of December 1933, massive flooding occurred sending many inhabitants to death. A concrete river control dike in 1937 under Mayor Felipe Santiago and Congressman Norberto Roque was constructed to keep the violent surge of the river from eroding the town’s mainland.

*Translation :

“To end the dissipation,

by the eroding river, to the town’s doom;

according to superstition, a wicked gnomic one,

misguided belief, ye must be obeyed.”

“Thus, it was christened Irosin,

they named and called the town as such;

or it was thus to badger,

the baleful waters of the town of Irosin.”