pig’s ass, in a, prep. phr., not at all; "Yes you
will, --------------"

pigs eye, n., euphemistic name for the very prevalent symbol
for the female pudendum, an upright diamond with a longitudinal slit
in the middle. “In a pig's eye" was used by some in preference to the
preceding saying, but to those conscious of the yoni sign the
improvement seemed hardly noticeable.

1942. Supplement to Rural Dialect of Grant County, Indiana, in the
'Nineties by William L McAtee.   p.7. Privately published booklet.


See here: https://archive.org/details/1945-to-c-1960-w-l-mcatee-and-his-printed-booklets/page/n3/mode/1up?q=pig%27s+eye