People often attribute the origins of the title She Stoops to Conquer to a work by Aphra Behn that was written in the mid-seventeenth century, but an examination of this text reveals no use of the word "stoop." There is a line that reads as follows:
Do! despise the Man that lays a Tyrant’s Claim
To what he ought to conquer by Submission.
Though not an exact phrasing, this line does present a similar concept of rising in circumstance through acts of submission.
Poet John Dryden also used a similar phrase in Amphitryon in 1690:
The prostrate lover, when he lowest lies,
But stoops to conquer, and but kneels to rise.
Oliver Goldsmith seemingly lifted the phrase to use as the title of his play around a hundred years later. The phrase has become an idiom in the English language, meaning someone who accepts a role, position, or behavior that is viewed as being "beneath" one's abilities but achieves some greater purpose.
In the work by Goldsmith, Kate Hardcastle manipulates Sir Charles Marlow by "stooping to conquer" his affections. She recognizes that he is often uncomfortable around women of higher social classes but at ease around those of a lower class. She therefore pretends to be a barmaid in order to make him more comfortable and observe his natural demeanor
The term "stoops to conquer" gained momentum likely because it presents an interesting paradox of imagery; at first, it might seem impossible to conquer by making oneself seem less. Though the line first appeared in works by Dryden and Behn, Goldsmith arguably popularized it with his own comedy.