Jack Rice noun used as a notional figure in descriptions of large objects AUSTRALIA,1945 From the name of a famous racehorse.
He may even be fortunate enough to have a roll Jack Rice couldn’t jump over. — Sidney J. Baker, TheAustralianLanguage, 1966
[T]he name was probably a tribute to that prince of hurdlers whose exploits gave rise to the expression, “so big that Jack Rice couldn’t jump over it”. — Joe Anderson, WinnersCanLaugh, 1982