Green’s Dictionary of Slang

(UK Und.) carelessly dressed; thus backform. mab, v.

c.1698		B.E. Dict. Canting Crew n.p.: Mab’d up, Drest carelessly, like a Slattern, of such a one it is said. Her Cloths fit on her, like a Saddle on a Sow’s Back.
1725		New Canting Dict. [as cit. c.1698].
1838		W. Holloway Dict. of Provincialisms 106/1: To Mab, To dress in a careless, slatternly manner.