Stories We Like: A Guide to the Comma
mid-15c., abbreviation of master (n.); also see mister. Used from 1814 with a following noun or adjective, to denote "the exemplar or embodiment of that quality" (e.g. Mr. Right "the only man a woman wishes to marry," 1826; Mr. Fix-It, 1912; Mr. Big, 1940). The plural Messrs. (1779) is an abbreviation of French messieurs, plural of monsieur, used in English to supply the plural of Mr., which is lacking.