Mrs., first recorded in the early 17th century, was originally, like Miss, an abbreviation of mistress.Mrs. and mistress were at first used interchangeably in all contexts, but by the second half of that century, the written form of the abbreviation was largely confined to use as a title preceding a woman's surname. By the early 19th century, reduction of the medial consonant cluster had contracted the usual pronunciation of the title from [mis-tris]/ˈmɪs trɪs/ to [mis-is]/ˈmɪs ɪs/ or [mis-iz]/ˈmɪs ɪz/. The contracted pronunciation used other than as a title was not considered standard, and today, locutions like Let me discuss it with the missis are perceived as old-fashioned. Currently, two main types of pronunciation for the abbreviation occur in the United States; [mis-iz]/ˈmɪs ɪz/ and sometimes [mis-is]/ˈmɪs ɪs/ are the common forms in the North and North Midland, while in the South Midland and South, the prevalent types are [miz-iz]/ˈmɪz ɪz/ and [miz]/mɪz/, the latter homophonous with the usual pronunciation of the abbreviation Ms.
1580s, abbreviation of mistress (q.v.), originally in all uses of that word. The plural Mmes. is an abbreviation of French mesdames, plural of madame, used in English to serve as the plural of Mrs., which is lacking. Pronunciation "missis" was considered vulgar at least into 18c. (cf missus). The Mrs. "one's wife" is from 1920.