It's a somewhat humorous misappropriation of a mathematical term being applied conceptually.

Roughly speaking, a Fourier transform takes as input a signal (like audio) and produces a spectrogram (the signal's component frequencies).

So "Idea Fourier" is a roundabout way of saying "take the component ideas from a statement". But really, GP just suggested making inferences or deductions, which has nothing to do with Fourier transforms.