As this is a Gaeltact village, the Irish Leitir Móir is the official name.
Lettermore (Irish: Leitir Móir) is a Gaeltacht village in County Galway, Ireland. It is also the name of an island, linked by road to the mainland, on which the village sits. The name comes from the IrishLeitir Móir meaning great rough hillside (leitir = rough hillside). The main spoken language of the area is Irish. Lettermore island is in two halves. The eastern half is known as Lettermore, while the western half is known as Lettercallow (Leitir Calaidh, "rough hillside by a marshy area").