An Etymological Dictionary of the German Language/Maulbeere
Maulbeere, f., from the equiv. MidHG. mûlber, n. and f., ‘mulberry,’ which originated, by differentiating r to l, from OHG. mûr-beri, môr-beri, n. The fluctuation from ô to û in OHG. indicates that the word was borrowed from Lat. môrum, ‘mulberry,’ môrus, ‘mulberry tree,’ whence also Du. moerbes, AS. and MidE. môrberie and mûrberie, MidE. also mulberie, E. mulberry.