They used two cars, both 1966 European versions. It was an English or possibly American term which found its automotive application in Europe, especially in Italy. This was written by John Hertzman and posted to the Alfa-Digest. Osso di Seppia means cuttle fish in Italian. The photo on my front page shows the beautiful Round-tail.
People think that the rear end looks like that.
Personally, I'm not that keen on the nick name. The car is red of course, Rosso Farina. This color has a slight tone of orange, which makes the red color a bit light. Very attractive, indeed. In the '60s, the 501 was very popular on Alfas.