mistress

Where it comes from

Mistress ordinarily means a woman in authority historically; now also a woman in a continuing relationship with a married person. Middle English mistress came from Anglo-French mestresse or maistresse, the feminine form of mestre, master. Master ultimately derives from Latin magister, a chief, director, or teacher, built on a comparative idea of being greater. Mistress first covered authority, ownership, household management, and teaching.

How the meaning developed

Its sense of a woman in a continuing relationship with a married person became increasingly dominant, while master kept far more of its prestigious range.