Be/go/keep on about something - Idioms by The Free Dictionary
be/go/keep on about something
keep (going) on about someone or something
to continue to talk excessively about someone or something. I wish you would not keep going on about Tom and Jill. Don't keep on about my haircut. It's perfect!
be on about talk about tediously and at length. British informal
be ˈon about something (informal) talk about something; mean something: I didn’t know what he was on about. It didn’t make sense.
be/go/keep ˈon about something (informal, disapproving) keep talking about the same thing so that people become bored or annoyed: What’s she on about now? ♢ Don’t keep on about your terrible journey. It’s so boring.