To come to a realisation of thought. To have an idea appear all of a sudden.
Origin - The music played on the movie "Shaft" making a chika-chika-chow noise. Usually played after an exciting moment.
Detective Partner 1 - "Ive just realised! He didnt commit suicide, he was murded and there are prints all over the scene!"
Detective Partner 2 - "Chickachow!!!"