"something easy," 1863, American English, from cake (n.) + walk (n.). Probably it is in some way a 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"), even though its figurative meaning is recorded before the literal one (1879). As a verb, from 1904. This may also be the source of the verbal phrase take the cake "win all" (1847).