My father grew up in SE NC, and I grew up in MD. Dad called them "Sunnies", but had told me his father & brothers called them bream or brim. Dad knew they were Bluegills too. I also called them Bluegills, (being one of those anal fly fishermen ) and most folks I associated with in MD called them Bluegills or "Sunnies", but I occasionally met folks in MD, both natives & transplants who called them bream or brim. (Really just how they pronounce the word!)
IMO, as folks move around & get used to the local terminology, some adapt, others just stick with what they're heard growing up.
If my Dad & others had not mentioned "bream or brim" to me when I was younger, it's likely I wouldn't know how widely used it was.
My Dad's father, my grandfather, called LM Bass "Green Trout". He said "brim" to refer to Bluegills, but called all in that related family, brim. Crappies, he called "specks" and I remember him saying to me "ya all call them "Croppies"! A Pickerel to my grandfather was a "Jack" which is also a popular term in the south.
Actually, all the years I've been in and out of Texas (Houston and Dallas/Ft. Worth), I've never heard any of them refer to Sunfish as Bream.
If you worked/lived in TX and never heard the word "Bream" you must live under a rock and not get out much...
But they DID refer to all of them as an even more idiotic name ... "perch". ALL of the sunfish species were lumped together as "perch".
I showed them a picture of a REAL Perch, and they argued that Texas Perch were different.
perfect observations of how stupid it can be to try to have any reasonable conversations using "common" names of animals. At least quickly come to an understanding of what creature you are discussing using the correct binomial then agree to call it whatever you want...
Bluegill (Lepomis machrochirus)do belong, like almost every other fish pursued with hook and line, to the order Perciformes from which the name "Perch" is derived.
So to call what we commonly call a bass a Sunfish isn't entirely wrong, or to call a Sunfish a Perch isn't entirely wrong, it just doesn't mean anything useful.
Just north of where I grew up, around Chautauqua Lake in NY, they call both black and white crappies "Calico Bass" ... Who knows why.
If you think it's bad with fish, you haven't spent any time with insects...