In conversation with Peachum’s servant and criminal apprentice, Filch, Lockit satirically alludes to a conventional figure of medieval romantic poetry and literature: the Knight Errant.
FILCH. One had need have the Constitution of a Horse to go thorough the Business.—Since the favourite Child-getter was disabled by a Mis-hap, I have pick’d up a little Money by helping the Ladies to a Pregnancy against their being call’d down to Sentence.—But if a Man cannot get an honest Livelyhood any easier way, I am sure, ’tis what I can’t undertake for another Session.
LOCKIT. Truly, if that great Man should tip off, ’twould be an irreparable Loss. The Vigor and Prowess of a Knight-Errant never sav’d half the Ladies in Distress that he hath done.—But, Boy, can’st thou tell me where thy Master is to be found?
Here, Filch and Lockit discuss the legal convention by which women could “plead their belly,” or, in other words, avoid execution if they could prove they were pregnant. Filch notes that he has in the past arranged to save various women, perhaps on behalf of Peachum, by hiring a “Child-getter” to impregnate female criminals. However, this man has since been “disabled by a Mis-hap,” likely venereal disease. In his absence, Filch himself has had to assume the duties of the former "Child-getter," a task that requires “the Constitution of a Horse.”
Lockit acknowledges the value of the former Child-Getter, whom he claims saved more “Ladies in Distress” than any “Knight-Errant.” In popular literature of the medieval period, the knight-errant was a common character type: a wandering knight who would be expected to perform brave, chivalrous acts such as defeating monsters and saving maidens from villains. Lockit’s allusion to the figure of the knight-errant is satirical: a man who is employed to impregnate women before they go to trial can hardly be thought of as conventionally chivalrous. This allusion, then, satirizes London of the early 18th century, suggesting that the “Child-Getter” is that vice-filled era’s equivalent to the brave knight.
At the conclusion of the story, Macheath has been miraculously spared from the hangman’s noose and joins his friends and acquaintances in a merry celebration. In an extended simile, he compares himself to a “Turk” who is surrounded by women in a harem:
Thus I stand like the Turk, with his Doxies around;
From all Sides their Glances his Passion confound;
For black, brown, and fair, his Inconstancy burns,
And the different Beauties subdue him by turns:
Each calls forth her Charms, to provoke his Desires:
Though willing to all; with but one he retires.
Here, Macheath alludes to the figure of the Ottoman sultan, whose harem of women was an object of fascination for European artists and writers in the early modern period. “Like the Turk,” he is surrounded by “Doxies,” a derisive term for “women” similar in tone and meaning to “wench.” With so many beautiful women around him, his “Passion” is confounded—or, in other words, he feels unable to select just one woman. Each woman enchants him “by turns,” and he marvels at the variety of women available to him, “black, brown, and fair,” as each one "calls forth her Charms." Ultimately, however, he selects only one.
Macheath’s simile describes the scene presented to him at the end of the story, as the myriad women to whom he has promised marriage—including Polly and Lucy—have come to witness his execution and unexpected release. Just as the “Turk” he alludes to must ultimately pick one woman from among a harem, so too has Macheath finally made his decision, choosing to marry Polly. However, his simile calls his future faithfulness to Polly into question. The Sultan might pick another woman on a different day, and Macheath hints that he is “willing” to enter into a relationship with any of the women.
