1863, American English, from cake (n.) + walk (n.), probably in reference to the cake given as a prize for the fanciest steps in a procession in a Southern black custom (explained by Thornton, 1912, as, "A walking competition among negroes," in which the prize cake goes to "the couple who put on most style"). Its figurative meaning of "something easy" (1863) is recorded before the literal one (1879). As a verb, from 1909. This may also be the source of the phrase to take the cake (1847).
