a wandering away from the subject
During his lecture on the history of mathematics, he made a digression in which he talked about the amusing eccentricities of Isaac Newton.
dis (apart, aside)#gradi (to go, step, walk) (Latin)
because of depression. we move or wander away from the path or subject of remorse. READ AS dig-the-rest-on-n-on. YOU JUST KEEP ON DIGGIN THE REST THINGS xcept THE main topic (subject) dig+reason: if u go deep inside the reason, then what will happen that u will moved from the main subject. a small examle: like u gone to a mango garden to eat mango (main reason) but after going there when u say so many mangoes, u start calculating e