also AA, abbreviation of Alcoholics Anonymous, attested by 1941, American English. The group name was the title of a book published in 1938 by the founder, Bill W. From 1914 as an abbreviation of anti-aircraft guns.

affixed to a name, abbreviation of Modern Latin Artium Baccalaureus "Bachelor of Arts" (see bachelor), 1773, American English. British English preferred B.A., perhaps because A.B. was used in Britain to mean able-bodied on seamen's papers.

also a k a, aka, initialism (acronym) for also known as; attested in legal documents by 1935.

also a.m., 1762 in reference to hours, an abbreviation of Latin ante meridiem "before noon" (q.v.). Synonymous with "morning" by 1776. AM as a type of radio wave broadcast, 1921, abbreviation of amplitude modulation (see amplitude). Affixed to a name, an abbreviation of artium magister "Master of Arts," an abbreviation preferable in a purely Latin idiom; British English preferred M.A. (magister artium, 1730). In some old chronologies, a.m. is anno mundi "year of the world."