My family history tells of one William O'Bryan leaving his parent's home in Ontario, Canada in the late 1850s and marrying Mary Jane Stacy at Black Hawk, Colorado on 6 June 1864, under the name of William Bryant. On immigration he dropped the 'O' and added the 't' to make his Irish surname English. This would be the end of the 'Potato Famine era.' Did he change the surname to cover tracks, or did he change the surname to hide his ethnicity? I don't know.