From Wiktionary, the free dictionary
From Maandel (“laundry basket”) + -weis (“-wise”).
maandelweis
- in great numbers
2002 January 26, “Eng Klack fir eis Sprooch”, in Luxemburger Wort[1]:Mir hu maandelweis Ausdréck mat engem däitsche Gesiicht am Lëtzebuergeschen.- We have a great number of expressions with a German appearance in Luxembourgish.