An Etymological Dictionary of the German Language/Annotated/Maul
Maul (1.), neuter, ‘mouth (of beasts), muzzle’ (in Upper German Maul is also used for Mund, ‘mouth of men’), from Middle High German mûl, mûle, neuter, mûle, feminine (Middle German), ‘mouth,’ Old High German mûla, feminine, ‘mouth,’ also ‘beak’; Dutch muil, Old Icelandic múle, masculine, ‘mouth, snout’; Gothic *mûlô, neuter, ‘mouth,’ is wanting, but is authenticated by the derivative faurmâljan, ‘to muzzle.’ This word is an l derivative from the root mû, from which High German Mund, with a participle suffix. nþ, is also formed; see Mund.
Maul (2.), neuter, ‘mule,’ in Maultier, neuter, Maulesel, masculine, from Middle High German mûltier, neuter, mûlesel, masculine, yet ordinarily simply mûl, masculine and neuter, mûle, masculine, ‘mule,’ Old High German mûl, masculine; borrowed from Latin mûlus. From the same source Dutch muil, m muilezel, Anglo-Saxon mûl, English mule, as well as Old Irish múl, are derived.