Erin Go Bragh is an anglicized version of an Irish Gaelic saying "Éirinn go Brách." It means Ireland till Doomsday.
Ironically, this started out as the flag of Saint Patrick's Battalion in the Mexican Army. At the beginning of the Mexican-American War in 1846, a large group of Roman Catholics defected to the Mexican army. They were mostly recent immigrants and mostly Irish.
Most of the defectors were recent Irish immigrants in the US that did not yet have Irish citizenship. The Mexican army offered them higher wages and Mexican citizenship. One of the flags survived, but it was allegedly stolen from the chapel at West Point sometime after the war.
By the 1860s the flag was in general use by Irish immigrants in the United States.
The flag is 3'x5' and made from a premium 100 denier polyester. It has a white header with two grommets. There are four rows of stitches on the fly and two rows on the top, bottom, and header side. The image is screen printed and appears on both sides. Writing will be reversed on the back.
3'x5' flags are 3 feet x 5 feet, 36 inches by 60 inches, 91 cm by 152 cm, 1 yard by 1.7 yards. This is the most common size flag you see hanging on porches, small flag poles, hanging at festivals, and inside of bars and restaurants.