Psst! ESC!

G'day from Aussie,

we don't have any strange phrases down under, but what about this bonza old pommy one

anyone got any ideas?
Cheers, Pete

It sounds from this definition that it is a rhyming variation on "not on your life."

NOT ON YOUR NELLIE! (OR NELLY) - " 'Not on your life!' An intensive tag, dating since the late 1930s. Used by, e.g., Frank Norman in his very readable 'Bang to Rights,' 1958. Short for 'not on your Nellie Duff!'; and 'Nellie Duff' rhymes on 'puff,' breath, breath of life, life itself." From Dictionary of Catch Phrases: American and British, from the Sixteenth Century to the Present Day by Eric Partridge, updated and edited by Paul Beale, Scarborough House, Lanham, Md., 1992.

Isn't Partridge's book wonderful? But now that we both have it, how shall we avoid duplicating each other's labors?

You can be the designated Partridge source.