@hatter @thomasfuchs LOL, yeah I think they were generally called "sidecar" expansions, which makes the name of the Amiga Sidecar extremely funny. The MacCharlie was a brilliant name that told you what it was without outright saying "IBM" or "PC" or "MSDOS".
(At the time, IBM's PC advertising featured a Charlie Chaplin knock-off.)
The Amiga "Sidecar"? What the heck were they thinking even? Ah, it's a total mystery how Commodore went bankrupt...