Ma'am

google

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mid 17th century: contraction of madam.

wiktionary

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Contraction of madam.

etymonline

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ma'am

also maam, 1660s, colloquial shortening of madam (q.v.). At one time the ordinary respectful form of address to a married woman; later restricted to the queen and royal princesses or used by servants to their mistresses. In U.S., used especially in answers, after yes or no.