To be in one’s particular specialty or to one’s precise taste. The word alley has long been used for one’s special province; Francis Bacon so used it in his essay Of Cunning (1612): “Such men . . . are good but in their own Alley.” Up one’s alley, however, is a twentieth-century turn of phrase. Margaret Carpenter used it in her novel Experiment Perilous (1943): “It isn’t up my alley at all.” See also not my cup of tea.