I cannot count the number of times that I've been showing a home, mention a FROG, and get really funny looks from our clients. 

It seems that none of our out-of-town buyers have ever heard the term.  But since we're both Charleston natives, it's just part of our language.

So, a FROG is a Finished Room Over Garage.  Other places refer to it as a bonus room, but here it's a FROG.

In the early 1970's, builders in the Charleston area starting dropping the ceiling in the garage to create space for a room - sometimes unfinished (UnFROG) and sometimes finished (FROG) in order to add value to their homes. The only access to this room was typically through the garage or laundry room.  This room is unique to Charleston -- at least by this name.  We also have the only MLS that identifies a FROG and FROG sqft. 

In more recent years, builders determined that it added even more value to their homes if the room was accessible from the upstairs hallway of the rest of the house.  The room would then be considered a bonus room.

So if you can access the room over the garage through the main house, it's technically a bonus room.  But we'll still call it a FROG :)