My own family fled Hercegovina for Montenegro in the 16th century & raised the Serb flag in Herceg Novi. Today, I know of people with my last name — some who are Orthodox, some who are Catholic and some who are Muslim.
Yeah, lots of movements back in forth in that area over time. Most of Montenegro (area around Niksic) was actually part of Hercegovina until 1878 (known as Stara Hercegovina). Most Serbs from Glamoc, Bosansko Grahovo, and the Knin-Vrlika area are those from that part of Stara Hercegovina, the Vlaski kraj.