What does O'Brien mean?
O'Brien /obri-en/ [2 sylls.] as a name for boys is of Celtic, Irish and Gaelic origin, and the meaning of O'Brien is "high, noble". O'Brien is a version of Brian (Celtic, Irish, Gaelic): could also mean "strength". Compare last name Obrien.
How popular is O'Brien?
O'Brien is a rare first name for men. O'Brien is an equivalently unique surname too for both adults and children. (2000 U.S. Census)
Below is a graphed comparison of the usage of O'Brien and corresponding names. Brain, Brian (#168 last year), Brien, Bryan (#148), Bryant (#581) and Bryon are the prominent related forms of O'Brien (not ranked) ranked in the Top 1000. Forms like Briant are uncommon. These boy names were at the top of their popularity during 1970-1979 (usage of 0.5872%) and have become significantly less popular since (usage 0.3505%, down 40.3%), with the forms Brain, Bryant and Bryon becoming less trendy. Brian (#168) and Bryan (#148) are two of the more chic boy names here. (2014 Birth Statistics)