pickelhauben.

pickelhaube (n.)Prussian spiked helmet, 1875, from German Pickelhaube, from pickel "(ice)pick, pickaxe," + haube "hood, bonnet." But the German word is attested 17c., long before the helmet type came into use, and originally meant simply "helmet;" Palmer ("Folk-Etymology") reports a German theory (Andresen) that it is a folk-etymology: "as if from Pickel and haube, a cap or coif[;] more correctly written Biekelhaube, [it] is for Beckelhaube, a word most probably derived from becken, a basin."