An Etymological Dictionary of the German Language/Annotated/Pilz
Pilz, masculine, ‘mushroom, fungus,’ from the equivalent Middle High German büleȥ (bülȥ), Old High German buliȥ (Modern High German i for ü is Upper German and Middle German, as in Kitt); a specifically German loan-word (compare Low German bülte) from Latin bôlêtus (Greek βωλίτης), ‘mushroom’; probably naturalised in German before the 7th century, as may be inferred from the permutation of t to z (for Latin ê, represented by Old High German î and ĭ compare Kette and Münze). Its rare occurrence in Romance (Grisons bulieu, French bolet, Vosges bulo) supports the very early adoption of the word in High German (compare Pfühl).