Cabusao used to be a barrio of Libmanan and it took several years before Cabusao became an independent town and parish.   This was because, although even in the early 19th century was already a thriving community because of its rich fishing grounds, its nearness to the town and parish of Libmanan which was bigger and more established, somehow, delayed its own transformation into a town.   After all, the parish of Libmanan could easily serve the spiritual needs of the people and the people of Cabusao did not really find it hard to go to the poblacion where most of them go anyway to transport and sell their products.

     Originally, the name of the town was Nabuhan, How it got the name Cabusao, it is agreed, is due to this story.   Way back in the early 1800's when place was still sparsely populated, a group of civil guards was sent to this sitio to conquer the place and to collect tributed for the government of Spain.   The leader of the guards was called "cabo" or "cabu", the Spanish term for corporal, who, upon reaching the place to accomplish their missions was met with indifference by the natives due to their fierceness in collecting taxes.   On account of this, he was mauled by the natives and his body was hurled to the water to the extent of almost drowning him. The term for this act in the local dialect is "sinaw-sawan sa tubig".   As the years went by, the word was contracted to "saw-saw" and this was added to "cabu" to designate the place as where a cabu was soaked in water.   From this the name Cabusao emerged.

     The parish is dedicated to the patronage of St. Bernardine of Siena.   The present church and convent of the parish were built through the efforts of Very Rev. Msgr. Manuel C. Ricafort.

Kami na sadit na parokya ni San Bernardino de Siena, sa tahaw kan mga namanang mararahay  na kaugalian asin natural na yaman, huri sa tamang teknolohiya, labi labing pagtios, dai pagkasararong institusyon na nagreresulta sa pagbaba kan dignidad nin tawo asin maluyang pagtubod.

Nagmamawot nin pusog, nagkakaminorootan, mauswag na simbahan, sarong komunidad nin mga disipulos na nagsusunod ki Kristo, nagsasabuhay, naghihiras asin nagbabalangibog kan tataramon nin Dios orog na sa mga dukha,

Sa tingraw kan liwanag nin Espiritu Santo asin sa inspirasyon ni Ina siring man ni San Bernardino de Siena, kami minadusay sa:

-pagmukna nin sadit na kristiyanong komunidad na nagpapahayag nin kapanoan nin buhay.

-mga pormasyon na makatao, makabayan asin maka Diyos;

-responsableng pangataman asin paggamit kan natural na yaman.