Thread:Sentry 616/@comment-3391158-20170826160736/@comment-25936766-20170826172331

GreyStark wrote: It means "descendant from" O'Brien for example is descendant from Brian. "Descendant of " (or "Descended from"). Aside from that, ^^^^^^^^^^^^^^^

It makes sense to me. It's not the lack of sense. It's the "explanation" given by Malcom which makes it sound like he doesn't actually know what it is beyond "Irish/Scottish".