my foot

Interjection

Meaning

(idiomatic) Indicates disapproval, disregard, disdain, disgust or disbelief.
Aerodynamics, my foot! The thing drives like a billboard.

Used other than figuratively or idiomatically: see my,‎ foot.

Source: en.wiktionary.org

bah nothing pshaw like hell my arse my ass your ass my neck my rear my eyeball harumph

Pro Se Filing Of The Day: ‘Motion To Put My Foot In Your Ass’ Source: Internet