OK, here's (a large part of) your answer. About 30 years ago Julian Griffiths & Rob Shackleton started doing some trips to go cave diving in Greece. In those days it was relatively uncommon for overseas cave diving trips to take place by CDG members, so contact with foreign cave divers didn't happen too often. They came across the use of inner tube loops as line belays by other cave divers, realised it was a superb idea and started using it here in the Dales. Around then Geoff Crossley started diving with these two and I'm pretty sure it was Geoff who came up with the name. (Shortly before Geoff used this name Clive Westlake referred to it as the "Crossley inner tube ploy" in a CDG Newsletter.) So - the most likely way you can get to the bottom of this is to ask Geoff if you ever bump into him. These days you're more likely to meet him flying around the Dales with a parapente than swimming about in a sump.
Of course it wasn't long before inner tube loops were being used for other purposes by cave divers; "dry" cavers soon cottoned on to their usefulness (see an article by Dave Elliott in a BCRA publication in the 1980s) and the rest, as they say, is history.