I have to say I'd agree with those who say "go with what the writer wrote".

A piseóg/pisreóg really has more the cadence of "an idiotic superstition" in normal usage. People tend to say dismissively of something like ... oh ... saying "God bless it" automatically after someone says "What a beautiful day", that it's "a bit of a piseóg". The sense is that it is a superstition, or a belief coming from ancient misunderstandings.

Still, I like the idea (if it's not happening to me, of course) of his mad mind attacking him with a thistle. Way hey!