A lady's maid, or ladymaid. Abigail, wife of Nabal, who introduced herself to David and afterwards married him, is a well-known Scripture heroine (1 Samuel xxv 3). Abigail was a popular middle class Christian name in the seventeenth century. Beaumont and Fletcher, in The Scornful Lady, call the “waiting gentlewoman” Abigail, a name employed by Swift, Fielding, and others, in their novels. Probably “Abigail Hill” the original name of Mrs. Masham, waiting-woman to Queen Anne, popularised the name.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894