An Etymological Dictionary of the German Language/Annotated/Maulbeere
Maulbeere, feminine, from the equivalent Middle High German mûlber, neuter and feminine, ‘mulberry,’ which originated, by differentiating r to l, from Old High German mûr-beri, môr-beri, neuter. The fluctuation from ô to û in Old High German indicates that the word was borrowed from Latin môrum, ‘mulberry,’ môrus, ‘mulberry tree,’ whence also Dutch moerbes, Anglo-Saxon and Middle English môrberie and mûrberie, Middle English also mulberie, English mulberry.