Green’s Dictionary of Slang

1. a cupboard [rhy. sl.; ult. nursery rhyme Old Mother Hubbard].

1960, 1975		Wentworth & Flexner DAS.
1971		J. Jones Rhy. Cockney Sl.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

2. (US) a shroud.

1904

C. Connors Bowery Life [ebook] W'en yer die, yer can't take it wid yer, kin yer? Dey ain't invented doze kind uv Mother Hubbards wid pockets in 'em yet.

3. nonsense, fanciful talk, lies.

1983

J. Sullivan ‘Yesterday Never Comes’ Only Fools and Horses [TV script] Don’t give me that old Mother Hubbard.