TO HAVE AN M UNDER (or BY) THE GIRDLE, verb. phr. (old).To have a courteous address. [By using the titles Mr., Mrs., Miss, etc.] See quot. 1850.
15978. HAUGHTON, A Woman will have her Will, vi. 2 [DODSLEY, Old Plays, 1874, x. 531]. Hark ye, honesty; methinks you might do well to HAVE AN M UNDER YOUR GIRDLE.
1605. JONSON, CHAPMAN, etc., Eastward Hoe, iv. 1. You might CARRY AN M UNDER YOUR GIRDLE.
1738. SWIFT, Polite Conversation, i. The devil take you Neverout . What plain Neverout! methinks you might HAVE AN M UNDER YOUR GIRDLE, Miss.
1850. HALLIWELL, A Dictionary of Archaic and Provincial Words, etc., s.v. M To keep the term Master out of sight, to be wanting in proper respect.