Green’s Dictionary of Slang

a loose woman, a slattern.

1632		R. Brome Covent-Garden Weeded I i: If I were forward as many Maidens are, / To wish a husband, must I not be sought? / I never was a Gadder: and my mother, / Before she dyed, adjur’d me to be none.
1850		E.V. Kenealy Goethe: a New Pantomime in Poetical Works 2 (1878) 336: Demirep, Lacedmutton, Gadder; / Do give over flinging dirt.
1859		Hotten Dict. of Modern Sl. etc. 43: gad, a trapesing, slatternly woman.
1864, 1867, 1870		Hotten Sl. Dict. [as cit. 1859].
1873		Sl. Dict.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 199: gad, an idle woman. ‘The old gad! She would do well to stay at home and take care of her child.’.
1915		Day Book (Chicago) 18 June 24/2: It’s a cinch that the girl who declares that she only married for a home has a reputation as a gadder all over the neighborhood.