My guess is that it was just a name that sounded good at GG.
It is in fact harder than many realise to come up with a name that fits and yet hasn't been used.
Henry Shires named the Contrail after the white line you see behind a plane in the sky, sometime the only man made thing you see on the trail.
Yet some unkind people thought it stood for Condensation Trail
(the ProTrail is a play on words with Contrail...)