köken: Past participle of the rarer verb bekloppen (“to hit on", "to percuss”), thus “insane as if beaten in the head”. Related to kloppen (“to hit”), the Central and German Low German form of klopfen (“to knock”).
aile: bekloppt sein, Bekloppte, Beklopptenschule, Bekloppter, Bist du bekloppt?, völlig bekloppt, völlig bekloppt sein
köken: From Middle Dutch geck (“madman”). Earlier origin uncertain, but perhaps from an imitative verb also found in Swedish gäcka (“to mock”). Cognate with German Geck, Jeck, English geek (see etymology there).
aile: gek als een deur, gek als een ui, gekke Henkie, gekkerd, gekkig, gekmakend, gekscheren, knettergek, stapelgek