An Etymological Dictionary of the German Language/Annotated/Knoblauch
Knoblauch, masculine, ‘garlic,’ from Middle High German knobelouch, masculine, with the original variant klobelouch, masculine, Old High German chlobolouh, chlofolouh, chlo volouh, masculine; with regard to b for f, compare Schwefel; the kn of the Middle High German and Modern High German words may be explained as in Knäuel by a process of differentiation, i.e. the l of the next syllable produced the change of the first l into n, compare Modern Dutch knoflook and Middle Low German kloflôk. In the ordinary explanation of ‘cleft leek’ no regard is paid to the fact that the first part of the compound, which is identical with Modern High German Kloben, appears elsewhere in the Teutonic group, Anglo-Saxon clufe, English clove (of garlic), Anglo-Saxon clufþung, ‘crowfoot,’ clufwyrt, ‘buttercup.’