A client recently told me he'd seen on one and the same menu in Greece both red mullet (rouget) and red muller (?). Can anyone confirm that both exist ? I suggested a typing error but he claims not. Does anyone know what red muller is ?
Since it appears in no dictionary or encyclopaedia with this sense, and as the typo explanation seems so reasonable, I think the onus is on your friend to justify why it is not an error. Translated menus are quite notorious for their errors; I've seen "rice" written as "mice" on a Greek menu. As Greek uses a different alphabet, errors are all the more understandable.