Malarkey (n.) also malarky, "lies and exaggerations, humbug," 1924, American English, of unknown origin. It also is an Irish surname. Meaning much the same thing at about the same time in U.S. slang was ackamarackus
Source : Online Etymology Dictionary
Note: The Online Etymology Dictionary maintains a free-access list of the origins of thousands of English words, a significant proportion of which are unknown