Maentwrog means "Twrog's stone". According to legend, a giant known as Twrog hurled a boulder from the top of a hill down into the settlement, destroying a paganaltar. This stone is said to be the one located in St Twrog's Church courtyard. It is said that if one rubs this boulder one is fated to return to the village in the future. The name was already in existence before the 12th Century as, according to a story found in the Mabinogion, Pryderi is buried "at Maen Tyfiawg, above Y Felenrhyd" after being killed by Gwydion in a battle at Y Felenrhyd on the banks of the River Dwyryd about a mile from the town. The boulder supposedly hurled by the giant is also the one said to mark Pryderi's grave. An alternative source, the 'Stanzas of the Graves' from The Black Book of Carmarthen, states that the grave is at Aber Gwenoli which is located in the woodland now known as Coed Felinrhyd just above Y Felenrhyd.
History
The church is dedicated to the memory of Twrog, an eminent British saint, who lived in the 5th and 6th Centuries. According to information in St Twrog's Church, based on a late addition to the Bonedd y Saint, there were four brothers and sons of Ithel Hael o Lydaw who came to Wales as Christian missionaries:
Saint Tanwg is the founder and patron saint of Llandanwg;
Saint Tegai is the founder and patron saint of Llandegai;
Saint Twrog is the founder and patron saint of Llandwrog and of Maentwrog.
The village settlement expanded in the 19th century to house workers from local slate mines. Within the village community is the imposing Plas Tan y Bwlch, home of the Snowdonia National Park Study Centre and former residence of the Oakeley family. Maentwrog hydro-electric power station was opened in 1928, and still produces electricity today. It is supplied by water from Llyn Trawsfynydd, a large man-made reservoir located near the village of Trawsfynydd. The power station produces electricity for the local Welsh Power network while controlling the level of the water in the lake to protect the local wildlife on the lake shores. The station has 2 turbine sets, capable of producing approximately 32 MW, the head of water being roughly 180m.
, the poet and biblical translator, born in nearby Llandecwyn, was rector between 1572 and 1624 and is buried inside St Twrog's Church. Thomas Love Peacock lived at Maentwrog in 1810, and subsequently married Jane Gryffydh, daughter of the parson. The British astrologerRussell Grant lives in nearby Tan-y-Bwlch.