"Erin Go Bragh" is Gaelic for the saying "Ireland Forever!" or "Ireland Until Eternity!". It is often used during Saint Patrick's Day. Singer Dick Gaughan recorded a song using the phrase as well. During the holiday the saying can be seen on mugs, t-shirts, and flags.Merriam-Webster Online Dictionary: Erin Go Bragh
History
While the exact origin of the phrase "erin go bragh" in uncertain, its use is known to date back to the 18th century. Used by those who supported the plight of the country's independence, it became anglicized into an English version in the late 1700s. Another documented use of the phrase occurred in Mexico during the presidency of Harry Truman. One of the Mexican infantry companies that was captured during the war with the United States featured the phrase on their unit's flag, along with an image of Saint Patrick on the reverse side.Flags of the World: Mexico: Batallon de San Patricio
Quote
"My name's Duncan Campbell from the shire of Argyll I've travelled this country for many's the mile I've travelled through Ireland, Scotland and a' And the name I go under's bold Erin-go-bragh" - first stanza of "Erin Go Bragh" by Dick GaughinDigital Traditions: Erin-Go-Bragh