Still not sure what the phrase means tbh.
A direct google translation comes back with "disabuse you idiot"
So maybe it means "idiot proof"?
A direct google translation comes back with "disabuse you idiot"
So maybe it means "idiot proof"?
So "couillon" is a synonym for balls and idiot if I'm understanding the GP's references correctly.
Contrary to "couilles", which are indeed "bollocks", "couillon" has no exact english synonym. Closest I can imagine, in spirit, would be "bollocks-brained", or "nutcase" which also carries the anatomical undertone.
So, "un détrompe-couillon" could directly translate as "a foolproofer" - though that translation is tamer than the original for lack of testicles.