What is the word for the abbreviation Mrs?

Mrs. is an abbreviated form of the Word Mistress that came into popularity as an abbreviation in coresspondance in the late 1500's. The Word Mistress is the feminine of the Word Master and was used to denote the formal position of the wife as keeper of the house. (If one was not married the title was used of the bachelors mother or unmarried sister if they resided in the same house.) The abrreviation later came to be used only for women who are married or widowed.

Another answer:

In the current day, Mrs stands for " Misses ".