Where the name Gallagher comes from?

Gallagher is an Irish surname of Gaelic origin. The name is derived from the Old Irish word "Ó Gallchobhair", which means "descendant of Gallchobhair". Gallchobhair was a personal name that was composed of the elements "gall", meaning "foreigner" or "stranger", and "cobhair", meaning "helper" or "supporter". The name Gallagher was first recorded in Ireland in the 12th century, and it is now one of the most common surnames in the country. The name is also found in Scotland, England, and the United States.