Hmmmmm......I'll be one of the first to swallow my embarrassment and pride and admit that I forgot what I used to know from reading Road And Track and Sports Car Graphics back in the 60s when some of the classic writers were still around.
I could Google it I suppose, but.....
But I'm afraid my mind is shot on shooting brakes, as much as I hate to admit it
I should add that I believe that it's a Brit term; and having owned an Austin Healey 100-6 and an MGB AND two Brit bikes. I.......gads it's embarrassing