1950, with -ism + name of U.S. Sen. Joseph R. McCarthy (1908-1957) of Wisconsin, leader of U.S. anti-Communist agitation. He entered the Senate in 1947, but his rise to national attention began with a widely reported speech on Feb. 9, 1950, in which he claimed to have a list of known Communists working for the State Department. The term is said to have been coined by Washington Post political cartoonist Herbert Block ("Herblock") in an editorial cartoon from March 29, 1950. The Army-McCarthy subcommittee hearings in the U.S. Senate ran from April to June 1954.
The surname is from Irish Mac Carthaigh "son of Carthach" (Welsh Caradawc), an ancient Celtic name, also known in its Latinized form, Caractacus (last of the British leaders to resist Rome, captured 51 C.E.)