A euphemism for in a pig's arse.
in a pig's eye
- (idiomatic) Under very unlikely circumstances; probably never.
2011, Izzy Auld, chapter 64, in Aggie's Double Dollies, ISBN 978-1-4620-2496-4, page 366:
- “Then he planned to kill you, and take over himself as governor.” “Hah, in a pig's eye,” said Nasty Three.
very unlikely, probably never